Whenever I make a gel painter with either the custom FGD or the official beta authoring tools, the gel wont stick to whatever surface is beneath it. So gels are useless for me, is there something i'm doing wrong? I have tried making the surface below the gel dropper a func_detail with no effect.

Go to map properties and change the value of 'Paint in map' to Yes.

Seriously, use your eyes before posting a new thread. This thread was 3 down from yours.