Thankfully I don't have to do the sanding , priming and painting on this one because I'm having a very hard time with MDF.
I can't seem to seal it. I have tried Shellac, tons of it, and I have tried polyurethane. Both just keep sucking up and never stop or eventually make a mess and caused the machined areas to bubble pretty bad. I've only tried spraying it, I hadn't used a brush yet.

My best luck was with Ruddy Brown Spray Primer I had laying around. I did a sign with that for another friend then sanded the top smooth and it left a nice deep brown down in the grooves.
Any hint's would be nice.

Richard