There is a free kit trigger but it depends on OS and you will have to learn how to use it because EZ drummer it is not! it is called KT Drum trigger.
There are also two free demos out there: apTrigga2 demo and another .... Don't know whether I should really saying this but Slate Trigger EX is available as a demo but with a very limited but extremely amazing sound set, you don't have the option to save anything but, just for that session, you get an idea of how good it it.
I was going to get Platinum Trigger myself but I got an SDx xgrade plus The Metal Foundry at 50% of usual price. Often though, with my previous point being a big example, alot of these drum softwear producers and resellers do some great deals. There are loads on at AudioDelux at the moment and some of them are electronic download so you save on postage, VAT, import duty and I can think of no better use of a certain $35... Metal Machine!
Othere than that dude, use the multiple outs and the 'Route Out' setting and tweak away. The link in my sig has a song that I used the basic kit on EZ drummer for, I'm not saying that what I did was great or anything and furthermore, it is a track I did about two years ago with next to zero knowledge (not that I have much now). All you need are some basic drum mixing knowledge which can be found anywhere really. There is an English article on the 'Sound on Sound' website with lots of information on how to mix extreme metal. Just google 'Mixing Extreme Metal' and it's there ... simples... You just have to realise you have got to work with what you have got and make the best of it.