Right now I'm building a small map to test out the Portal 2 features, unfortunately I encountered several problems using the new stuff. So far I've got the laser to work but I can't do much with it yet. I haven't attempted excursion funnels yet.

Please read the entire question before answering it, I'm not the most organized person when it comes to asking questions plus each question describes the problem itself as accurately as I can. That said if my description isn't clear enough just tell me what I need to clarify.
I've said this below but it's very important for the way I work so I'll say it here too - if you're giving a step by step description of what to do, please explain what each step does, this makes it easier for me to figure out what I did wrong if I make a mistake - e.g. if I read a step wrong. When I'm given a list of steps without an explanation of what they do I tend to do something wrong the first time because I don't know what I'm doing - and I have no idea what the mistake was so I can't fix it myself.

1. About gel: The gel dropping entity (paint_sprayer) crashes the game when I try to run the map - the compile finishes but then Portal 2 crashes. I've downloaded the example map from the developer wiki and copied the paint_sprayer properties from that map exactly however the gel dropper entity still crashes the game - if I remove it from the map or set it to default properties (which makes it do nothing, not very useful) the map will run fine - though the gel won't work obviously.
   Compiling and running the example map works perfectly so it's not a problem with my system. Can anyone walk me through the steps of inserting a working gel sprayer, and explain what each step does? (If I know what the step does it's easier to figure out what I did wrong when I make a mistake).

EDIT: To clarify this question, I want to know how to make a gel sprayer that runs automatically from level start, not a triggered one - unless making a triggered one is easier.

1. About aerial faith plates: the wiki tells me to use a trigger_catapult, however when I make a trigger brush entity and scroll through the list of trigger types trigger_catapult doesn't exist. Is anyone else encountering this problem? Or am I overlooking something obvious?

2. About cubes - I may have the answer to this already: The small map I'm working on is supposed to use 2 types of weighted cubes (including a laser redirection cube). The cubes render fine in the editor but they don't render in-game. However I'm not sure that I had set the entity type to prop_weighted_cube... if it was set to another prop type would it cause this problem? I'll check this when I get home this evening.

3. misc: This doesn't really have anything to do with the map I'm building right now but I'm curious about adding entities from other source games into a Portal 2 map (I've already tried this in Portal 1 btw). Does it have the potential to cause bugs/problems assuming that the person playing the map has the game the entity is taken from installed? I don't want to release a map like this if it will turn out to be buggy, but I have some interesting ideas for how to combine some game elements.

Thanks.

For Question #1, I haven't played around with the Gels yet but I was reading a tutorial on them earlier and there's a note here at the bottom:

Quote:
Go to Map -> Map Properties and set "allow paint in map" to yes and "max blob count" to 250.

This step is very important! Gels will not work without it!

Have you set this in the properties of your map?

I was using another tutorial that was very bare and didn't include that part.
I'll try again with that property set, thanks!
The tutorial you found is much better, too.

There are even more Tutorials on this Page. http://wiki.p2mods.com/index.php?title=Tutorials
I dont know if it can Help you with your faithplates but i?ll try to create a trigger_catapult and let you know if it worked

You guys should stop linking to that site, and start translating those tutorials to the VDC. It's the official mapping/hammer/Source editing wiki, there's a reason we closed our wiki and started pointing people to the VDC.