Undercoating
 

I'm from Rockville, MD anybody knows a nice shop for undercoating? or is it too late to DIY undercoating considering the temperature outside and the paint curing

What's the undercoat for? sound proofing? Just use dampening under your carpet.
If you're looking for weatherproofing, there's already a factor coat, and also rust warranty, so why bother?

for weatherproofing. thanks for the info