1. How long do I heat the plastic for? (how long does it take to sag 2 inches
About 2 mins, once the plastic starts to sag it drops quickly, you need to watch.
2. How hot does the oven need to be? (preheated)
About 200-220 celcius is ideal.
3. How long does the home vacuum need to be on? (how long do I leave the plastic on while the vacuum is on)
I turn the vacuum cleaner on a few seconds before putting the plastic on; and leave it for about 6 seconds whilst plastic is in place and formed; then leave for about 10 seconds more, when plastic is starting to harden but still supple, and carefully remove mold.
4. How long does it take the plastic to dry (polystyrene
A couple of minutes to cool - doesn't need drying as it is already dry and very hot out of the oven!
5. What paints do I use to get a glossy surface (I plan to use krylon fusion)
Krylon Fusion, or Plasti-Kote (which I use as I can't get Krylon in the UK). Plasti-Kote is excellent; and also has a very good plastic primer spray paint too.
6. Krylon fusion says I don't need to sand the plastic or use primer. Just spray on. is this true?
Depends on the surface - if it is smooth, then spray paint will not stick so well, so always best to use a primer - not worth not doing. If the paint however says you don't need primer, fine; but test on a spare sheet you can waste to see if it is ok; different plastics may need primer anyway - if in doubt though, use primer.