Originally Posted by tuxedocivic
I've always just primed and primed until the seams are primed! I use an HVLP and I'll concentrate the spray pattern and go along the edges. I can watch the primer disappear into the end grain but it eventually starts to show and then eventually is primed.
I did this and it seems to hold up so far.
Look for a high yield or high build primer. Then coat it well, multiple coats. Sanding in between coats in some cases.
If you use a fast drying primer and HVLP gun it's not too bad. Spray a few coats, sand it. Stop short of exposing MDF. Spray more, sand more. Repeat until you have the desired effect.
With any painted MDF or wood surface you will risk the possibility of long term cracking. Nothing you can do. Even the highest end painted kitchen cabinets have it.
MDF is better than normal wood in that it's more consistent, and the moisture content of pieces is generally the same indoors. But that is not a guarantee.
They have a cool method on cabinet doors where they coat MDF with thermofoil, and that seems to be the best alternative to painting. Thermofoil is a surface finish applied to cabinets and other stuff like that where they replace paint, and it's mostly used on top of MDF. It is some kind of a plastic material which is thermoformed to the profile of and MDF cabinet door.
From what I understand it is a thin, tight, heat-sealed plastic wrap used to mold over an MDF substrate. I am not sure if it is very DIY friendly as you need to heat it, or bake it to make it done right. Put your speakers in the oven? lmao.