I use a (heavy) vaccuum pump for veneering work in the shop, but lighter alternatives also exist. Here is a REALLY good product:

http://www.vacupress.com/products2.htm#compact100

Mind you, that's a whole veneering kit, but it's not too pricey. For your project, just make a thick plywood box to hold your gel container, put a lid on it, and put it inside the vaccuum bag. Pump it for a few seconds, then remove and pour.

Cheers