i have used herculiner alot works good with 2 coats.i believe por15 makes a undercoating too.

 

may be a dumb question but are you able to pull up new carpet without ruining it? the car I am buying has brand new carpet inside and I am going to be doing the undercoating and wanted to do the floor pans from the top but dont want to ruin new carpet.

 

onlything holding the carpet down is the seats and door sills.