K-36 is good , I use NCP -271 Corrosion Resistant Primer for the past 5 years , Make damn sure you use a charcoal respirator as this stuff is BAD !
Both Sand easy, Both have excellet fast build qualities. can be water sanded .
Needs a gun with a big nozzle for better spray out.
NCP 271 mixes 3 parts product to 1 part catylist , can be reduced with DT reducers up to 10% for slower drying , as every 10 deg. over 78* lessens the pot life buy 10-20 minutes .

Spray