I think your talking about Fusor. It's an adhesive, and will bond the kit to the car, but you may want to blend the kit to the car with fiberglass or something if you want it really smoothly molded. Urethane kits are kinda hard to mold because most resins used with fiberglass won't stick to it very well. Fiberglass kits are easy though. Lotta work though, lots of sanding and feathering with body filler. Depending on what type of resin you're using, you probably want to strip down to bare metal and then rough the metal up pretty good. You want to have the best possible adhesion, because the fiberglass will be more flexible than the steel, so you're fighting both peel and shear modes. Clean and degrease the sheet metal and the body kit, this is important also..