Give the m-d-f a light sanding to remove any surface imperfections. Pay special attention to raw edges, they should be sanded as smooth as possible to ensure a smooth paint finish.
Remove the dust with a tack cloth. For bigger projects a shop vac can really clear out that dust in a hurry.
Always, always prime m-d-f with a good quality primer. The primer will raise the grain of the wood slightly while it's drying so it almost feels a little prickly.
So, once it's dry you will need to sand it again with a fine sandpaper to bring the surface back to smooth.
The ideal finish coat on m-d-f is an enamel paint. The finish is strong and durable. As far as application, I like a small sponge roller for a smooth finish.
If you prefer to work with a brush, make sure that you choose a good quality brush for the best finish.
After the frist coat dries, you may or may not need to sand again, pull a nylon stocking over your hand and rub it over the surface to check for rough spots, and if needed use a superfine sandpaper to smooth it out before you put the final coat on.
Follow these simple steps and your m-d-f will have a great finish every time. I'm Mrs. Fixit and it's just that simple!
