ok, so i wanted to write a guide on how i think its best to attack with drags vs TH7 and TH8. It is possible, with a little luck to get 3 stars vs a lvl 6 air defence with lvl 2 drags- not always but with these strategies you can acheive it. Firstly i would like to cite coc builder article 2484 as a great starting point. However that article is a little old now and as COC continues to evolve, I do think i can expand on what is written there though with a few tricks and techniques i have learned and practiced myself.
Firstly, the basics as talked about in article 2484- NEVER ATTACK FROM A CORNER! secondly, use two 'book end' troops in order to make the funnel work (more about that below).
Dragons are simple creatures, moving from one building to the next setting it on fire. if you drop 10 dragons on a corner spot they wil nearly always split in 2 and make their way around the perimiter of a base getting picked of by defences- i have seen lvl 3 dragons 1 star a th7 base with 2 lvl 3 air defences before simply because the attacker dropped his drags from a corner.
'Book End' Funnelling:
The main part of a funnel attack is the placement of your first 2 troops the 'book ends'- their main objective will be to clear any side buildings to keep your main attack on track. they will will usually be consist of your Barbarian king and a single drag (or 2 drags if king is unavailable). If you are still upgrading your camps, instead of wasting a drag you can use minions or wizards to the same effect.
It is essential that these two troops are placed in such a way that they will clear out any side buildings allowing your main force to go straight through the middle of a base. Make sure to take out any corner builders first and ensure you drop the troops in such a way that they go around the edge rather than inwards towards where your main force will be attacking.
When scouting your target, if one end has more cannons, and the other has archer towers, it makes sense to send the dragon vs the cannons and king vs the archer tower.
Now for the attack itself:
OK firstly army over view: camps should be full with drags- no exceptions. For spells 2 rage 1 heal and poison if you have it available. Clan castle- if your clan has max (lvl 6) loons take them every time- if not get the highest level dragon available, if you have a level 4 clan castle get the highest level loon your clan has to accompany your dragon. whether loons or drag and loon in clan castle if you can receive a dark spell it should always be the highest level earthquake available to you.
Before you attack:
Scout the base and decide which flank you want to attack from, since the addition of air sweepers, you should almost always want to attack from behind the sweeper- this renders it useless and becomes one less thing to worry about in your attack. the only time you may ant to attack into the sweeper is if all 3 air defences are close together and at the opposite side of the core from the sweeper, this allows your attack force to take them out quickly with a rage and heal, however it is always a risk attacking into the sweeper.
If you have a quake spell, use it first- its much easier to use it at the start than have to worry about it mid attack. aim for the high hp buildings for maximum effect, usually you can get the Town Hall, Clan castle and one or more air defences in its radius speeding up the amount of time it takes your drags to go throught the base's core.
The next thing to do is to place your book ends, if the base has corner buildings make sure the book ends take these out 1st then move inside. allow the a little time to take out the first few buildings so your main dragons only have central buildings to concentrate on.
After 5-10 seconds its time to send in the drags, drop them in a line in between where your book ends are clearing. Straight after the drags, send in you clan castle troops just behind them and directly inline with the nearest air defence. Let the drags destroy the first few buildings and move inside.
As soon as they are within range of the first air defence, drop a rage spell, drop it in front of the drags so they are just within its reach to maximise its potential- if you drop it dircetly on top of them you are wasting half of the spells radius on an area already cleared.
If the defending clan castle troops have deployed the next spell should be a poison if you have it available. No matter what is in the clan castle, raged drags and poisoned defenders should make this part a breeze.
By this point your drags should be somewhere over the centre or 'core' of the base, this is usually wher dragons and loons take the most fire from air defences, wizard towers and archer towers. Drop your heal where ever it can cover the most amount of dragons, if you have loons they will die quickly in the core so try to heal them too. as your troops pass through the core they will start to emerge from the other side of your rage spell, drop your second rage at this point, again drop it in such a place to maximise its radius whilst ensuring the drags are raged immediatley.
If you have followed these steps correctly you have a great chance that your dragons will come throught the base with enough firepower remaining to take out any other buildings for a 3 star attack.
Advanced Techniques and Unusual Base Designs:
Occasionally you may come across a base where standard funneling wont work.
The most common of these will have a third air defence away from the core and covered by a central air sweeper, for this type of base if you have loons available you can usually take the core as usual using 1 rage and the heal, and save your second rage to take the far air defence with loons. wait until your drags are close enough to distract the third AD then drop loons and rage as close as possible to it to take it out quickly.
Some bases completely seperate all 3 air defences, for this, try to use the king to clear surrounding buildings of the 1st ad then send 4 drags and a heal to take it out, for the second AD try to create a mini funnel with 2 drag book ends and 4 drags with a rageto take it out, then wait for drags to get close enough to distract 3rd AD before dropping raged loons as above.
These bases are much more difficult can be suscepltable to other attacks such as lvl 4 hogs or gowipe.