Painting glass

[threedee]

Anyone have any tips on painting glass ? Having trouble with uniform filling back engraved mirrors, takes many layers to fill in gaps left by the brush.
As if paint just wont stick to glass (duh... right)... Whole back has been washed in isopropyl alcohol to clean it. Tried brush, sponge(painting), sponge dabbing. Will be trying to drag fill later on.
Special, more sticky paints ? Some techniques i dont know about ? Spraying is a no, as no space to do it properly.

 

[pe2dave]

To engrave, they use some form of acid etch? Perhaps (if you can find some) that would leave
a more grippy surface?

 

[threedee]

Thats the thing,its laser engraved and pretty rough (well kinda like sandblasting), but i still cant seem to put down a nice looking fill on it.
My wife had tried hand in this yesterday with tiiiinyyyyy brush and it kind of works. Takes for ages to paint though.
Soft but big brush ?