Over the last few days I've been playing around with a scrap piece of MDF, some pink paint and some Minwax polyurathane. Here is the process I used for finishing Test Panel #1:
1. Sanded MDF with 150 grit sandpaper
2. Rolled on first coat of primer
NOTE: I used an OIL BASED primer because a water-based primer will soak into the MDF and ruin it!
3. Sanded with 150 grit sandpaper
4. Rolled on second coat of primer
5. Sanded with 220 grit sandpaper
6. Rolled on first coat of paint
NOTE: I used a latex, water-based paint (made by Behr) which is OK to apply after the MDF is sealed.
7. Sanded with 220 grit sandpaper
8. Rolled on second coat of paint
At this point I was completely unhappy with how it was coming out. I had multiple particles/hairs in the paint (probably from a bad roller) and there was an unmistakable "orange peel" texture all over the place that you could feel and worse yet see. I decided to change up my strategy:
9. Sanded with 220 grit sandpaper
10. Using a FOAM BRUSH I applied a third coat of paint.
11. Applied first coat of poly (Minwax) using the foam brush.
12. Sanded with 220 grit sandpaper
13. Applied second coat of poly using the foam brush.
14. Sanded with 220 grit sandpaper
15. Applied third coat of poly using the foam brush.
16. Sanded with 600 grit sandpaper
17. Applied FINAL coat of poly using the foam brush.
Here are the "before" and "after" pics:
Here are some extra (not so good) shots of the finished panel. The flash of the camera kind of ruins the pictures and I don't think you get a good sense of what it actually looks like unless you are standing next to it. The finish is still a bit streaky and there are a few spots where air bubbles in the poly dried leaving it a bit bumpy - you just can't see it in the pictures. That said, the bottom picture really makes the finished surface look like it is mirrored or something - check out the reflection of the paper towel! I assure you it doesn't really look like that up close.
I'm going to try a different method over the next few days on a separate panel and see if I can come up with something better. I haven't tried using a foam roller and since I kind of like the way the foam brush came out I'm going to give that a shot. I'm also hoping to talk to an actual painter or someone that works at a paint specialty shop and see what they think. I will be starting test panel #2 in a few days when I get a chance to buy a foam roller and some different supplies.
Thanks for looking!!