I'm experimenting with the idea of modding. I want to try to do something, but first I need to know what it is that makes the puzzlemaker add the portalcleanser brush to the vmf. I'm guessing its a script, but I don't know where to start looking. Does anyone know where I can find the script, if it exists?

All puzzlemaker items are instances. If you export it to hammer you can see which ones and you can look inside the instances by going into its' properties and click edit instance.

If you are trying to mod the editor, then BenVlodgi or FelixGriffin are the people you would want to talk to.

Ya, I am experimenting with modding the editor. I know that most pieces exported are instanced, but the actual fizzler brush is not, which surprised me.

Fizzler brushes, goo, walls and floors, panel brushes, antlines as well as faith plate triggers are all added by the puzzlemaker, and you can't change the exporter's behaviour. Carl Kenner's stylemod, now included in the BEE2, has the ability with a modded vbsp.exe to change all of these things though. It can switch fizzlers into paint cleansers, modifying the entities and switching instances. You definitely want to use it, it does a few other things as well.

ok, well if someone already has paintcleansers in another mod, then there is no real need for me to try too hard on this anymore. thank you. If anyone knows a way to mod that myself, I would still love to know, for the fun of it.

It's pretty tricky and pretty specialized. You need to write a C++ program that intercepts the map before it gets to VBSP and edits the appropriate brushes. I believe the excellent one Carl wrote for the BEE2 has options to change lots of different things, try sending him a PM.

A better way to mod fizzlers might be to use the "FGEMOD style," which hijacks the AngledPanel class to allow four different lengths. Look at the p2editor/fg_editor_mod/physler.vmf instance for an example.