Cabinet Paint Challenge

locofoco

Got a call from a nice young couple who bought a high end house ($400's)- contractor put in white pressed board cabinets (8 years ago)that are now chipping on the edges. Water gets into edges and swells.Problem isn't too bad yet.
I tried sanding entire doors lightly, bad spots a little more, primer then 2 coats of laquer. Bad areas were visible thru laquer.
My next experiment was prime bad spots,sand entire door,Then 1 coat SW Pro Classic W/Penetrol (brushed), lightly sand w/220 then finish coat of Pro Classic. Seems to cover damaged edges good. I'm amazed. Question is this - Do I need to prime entire door or just sand. I think the original finish was laquer. Will I have adhesion problems?? Trying to keep the price within reason. Also -what would you charge for 10 doors (base) and 16 drawer fronts?
I can't believe builder used this junk in that nice house!