primer / sealer...necessary?

i have painted cars with and without using it.what is the consensus here/

 

im not a painter by no means but ive been told paint over paint is ok but any bare places have to be primed.if im wrong im sure i will be corrected

 

With all the weird finishes out there and the 'hot' solvents/catalysts used in the new paints, I use a sealer. Cheap insurance.

 

Hey David, You can overreduce most epoxy primers for use as a sealer..........I would not shoot a finish over an unsealed surface especially given what automotive finish costs today! If you're shooting over an old finish be it oem & especially a reshoot, a sealer is a must.
If you choose to side step a sealer, don't act suprised if you get sand scratch swelling and/or colour bleed thru in your top coat

" Meanwhyle, back aboard The tainted Pork "