I actually had great success on three PS3s so far.
I made my own custom tool for the job.
It was originally a "Painter's scraper", if i translated that correctedly.
I used my Dremel with a sandpaper-attachment and sanded the end down till it was very thin and made sure to sand off the edges as well, so it would be thin, but quite blunt!
That way, even if you did manage to touch some of the internals under the IHS, it wouldnt damage it.
That took care of most of the overheating of my PS3, but didnt quite solve the problem inherent with the PS3 Slim design.
The PS3 Slim badly needs more holes to vent the heat, which is why even after delidding the fan spins up quite a bit when playing hardware-intensive games for a while. So i ended up adding holes to the top and bottom of the case to remedy that.
Thats the first one i did and while the end-result was a bit "rough" and nowhere as neat as i would have wanted it, it works beautifully.
The Fan never spins up more than its lowest settings. Not even in GTA 5 after prolonged playtimes.
I had to turn off the sound of my TV entirely while playing GTA 5 and listen real hard to even make out any noise at all. I couldnt be happier.
I used this video as a basic outline of how to do it: