I recently put together a stationary combination work bench and cabinets out of 5/8 particle board and 9/8 "benchtop" (which appears to just be thick particle board). I previously made a work table from the same "benchtop" and applied an oil-based polyurethane finish to it without issue. However I had some water-based polyurethane around that I wanted to use up, both in matte and satin finish, so I applied a coat of the water-based matte finish to my new tops.
To my surprise, the smooth face of the particle board became quite rough. Can I treat this like regular wood and just sand it back down before applying another coat of the water-based polyurethane, or do I need to try something else for my next coat?
The rough look of this combination work bench and cabinet is in this shot of the plans below, although I made a number of small changes on the fly and haven't updated the plans to match. The purple bits are intended to be slide-out drawers, and the teal bits are intended to be slide out shelves (that I'll probably mount at mixed heights), but I haven't built either of those yet.
Again, my question is about re-smoothing the "benchtop" particle board that the water-based polyurethane seems to have raised, whether another coat will cause more problems after I do so. (Or if I need to just cover it with a layer of hardboard.)
Also, I'm thinking of priming and possibly painting the rest of this cabinet; do I have to worry about raising the "grain" there?