I'm unfamilier with TremClad, but I use Majik from TSC and they sell a hardner that works with it. I think someone earlier posted a hardner that will work with TremClad.
Now if you want to get creative, we used to take single stage, spray 2-3 coats of it and then spray clear mixed with single stage, mixed with less and less color each coat. Wetsand and buff. Those paint jobs looked amazing.
You could also just try clearing over the TremClad.