Hello,
What are you using for the heater and vacuum?
A shop vac is never going to be particularly powerful. If you really want sharp details a tank/pump system is the way to go.
I've got a bit of info about my system here:
Vacuumtable - Workshop
Basically, I've got 2 10 gallon tanks and a Gast vacuum pump. The pump evacuates the tanks so when I open the valve you get a really strong pull really fast (it will collapse a spray paint can lid). The whole WHOOSH of vacuum takes about 1 second, so the seal has to be perfect on the first try or I'll lose the vacuum before I get anywhere.