Paint Questions

Ok ive bounced a few ideas off some folks. I recently shot my Scamp with Urethane Single Stage. Monster runs so I sanded it back down and its sat that way for a bit. I need to buy more paint... I was looking at buying Urethane Basecoat/clear system.


1. Will i have to seal the car before switching?

2. If i stay with the Urethane Single Stage I should be able to just prep it and shoot right?

I guess what I really dont understand is that if they are both urethane based paints why i would have to seal if I switched to the Urethane basecoat system.