I have done allot of casting, tried out every sort of resin and epoxy I could find. The best and least expensive (if you don't care about the color) is bondo fiberglass polyester resin.
It's like the environmental tech stuff but is stronger. The only drawback is that it it clear reddish purple. It's at least half the cost of anything else, it's not flexible but I haven't had any problems with it chipping (I make dice). It shrinks a little bit, and use it in a well ventelated area.
I haven't had too many problems with the ET stuff though, just give things a little extra hardener.
I don't know how well any of them would work with things like the tron handles. If you build up the backs of the handles with clay to make them thicker (perhaps allmost solid) it should work fine. If I was doing that I would mix something into the resin to stretch it and save money. I got really great results putting broken plastic bits into my resin (CD cases, taillight covers etc...).
Most hobby two part resins seem pretty brittle (Aluminite), and most casting expoxys are a bit rubbery. Epoxy glues work well but they shrink allot and take quite a while to cure.
Lasersoup- The latex rubber probably affected the cure of your resin, and the resin will probably destroy the rubber. That stuff is mostly used to make molds for plaster casts. I have used it and never got good results with resin. There aren't many replacements for silicone rubber that are any easier, you might be able to make a simple cast like that using a wax mould though. Small amounts of silicone are available from modeling supply stores, along with the special modeling clay that can be used with the silicone.
You could actually make a mold with allot less silicone rubber than Fozzy used, you only need about a 3mm layer of the silicone (enough to prevent tearing) and a support structure to hold it up (like the plaster he used). The thickener is not then needed, which will improve the detail of the cast. My favorite tip for this is to use Lego blocks to build a custom case around your mould, you can get it to a really tight fit, and then the Legos will act as a case to hold the whole thing while you are pouring.
For the trigger I would actually make a 1-part mould, simply make a slightly large sprue out of clay and support the trigger with it and then pour the silicone around it. When cured the silicone is fexible enough to remove the part through the sprute hole.
Another modeling process that would be of intrest is brass etching, you could easily make the light interrupter wheels for trackballs and spinners using this method.