What's the best way to put decals on an already textured surface? Or...if you have sections of brick wall and you want to add in one section where the bricks are busted up. Is the best/only to do that either to section off the wall and add in a separate brush with that texture...or for like a poster or sign, to make a super thin brush with caulk on all sides and the texture on the side facing where it's to be seen?

for posters and signs I just use the super thin with caulk... works great and it only cost 2 triangles to use! AS for the brick, I would say it probably would be best to section the wall off in the same manner as you would for a window.

I tend to find that the first method brutus offered is best in all cases. the super thin brush that is just one unit away from the wall.

If the texture is transparent, you will never notice that it is slightly away from the wall... not by one unit anyways. The caulk cant be seen, so there would be no edges or back for the player to see.

Cutting the wall will usually just create more brush divisions leading to higher r_speeds.