Ok, so I'm wondering how to make a rain/sprinkler system that's used in the near-end of the Wheatley battle to remove paint. But I can't find anything that may relate to this in Hammer, anyone know how to make it?

You need to use the appropriate particle effect to polish it, but to wash off the paint realistically, make some info_paint_sprayers set to water spraying wherever you want gel to be washed off, and then set them to "silent". Then you can trigger them.

Alternatively, you can use a trigger_paint_cleanser. This may be a little more efficient than multiple paint sprayers, and should be slightly less processor intensive. But you still need to use the particle effect, as Vordwann said.

Trigger_paint_cleanser doesn't take off paint after it has been applied to a surface. For that purpose use a water sprayer with "silent" set on and use some particle effects to make it look like it's raining/washing off.

Vordwann wrote:
Trigger_paint_cleanser doesn't take off paint after it has been applied to a surface.

Oh, okay. That's good to know.

So what is the right particle effect?

Look at the list of particles and try a few to see what works best. I'm not sure which was the exact effect used in-game at the end to clean the gel and put out the stalemate resolution annex fire, but I'm guessing it was probably sprinkler_jet, sprinkler_ring, or sprinkler_funnel in conjunction with water_wash. You could decompile the map if you really need to know exactly how Valve did it.

Yeah whatever was the washing effect on the ground did some ripple distortion.

Forget it, I am abandoning the idea. I was going to try to have rain wash paint for the entire map (which is already 12 Megabytes big and getting bigger) but I don't think it would work for this map.