The trigger pull on the AUG is a function of the plastic-on-plastic design, not a matter of lubrication.
The AUG was designed to be an ultra-modern assault weapon, and a good trigger was not part of the design concept.
I rather doubt any lube will help, and again, what lubes I'd recommend for a metal trigger unit may not play well with plastic.
If you insist, I'd look at a true synthetic grease.
I can recommend Super Lube grease, which is a Teflon bearing synthetic.
You can buy small tubes to try it from Midway:
http://www.midwayusa.com/viewproduct...tnumber=719267