Filling MDF screw holes

[brihyn]

Hey all-
Just want to see what collective advice I can get for filling the screwholes on MDF. I've started using Bondo based on the advice here, and everything feels smooth to the touch, but after painting I can still see the fills.
Anyone have great tricks to insure you have a perfectly smooth surface?

[Drnick]

Bondo is the way to go, the rest of it is time and practice.  I found that looking at it under a flat light (Lit from lamp at side not straight on) helped to see the bumps and ridges.  Unfortunately like you I also found that although it seemed smooth and flat under hand it wasn't so great with a few layers of paint. 

It goes something like this,  Rough fill hole, sand down, thin layer of filler,  Sand down to 1200 Grit using a block or orbital sander.   Hit it up with a good quality Primer, Sand, fill, sand, primer, Hopefully you then have good results.  In which case it's miller time

[brihyn]

great, thanks. i was thinking about taking a light to it, but wasn't sure if it'd help (and hadn't really considered the angle). Knowing your full procedure definitely helps as well.
That said, anyone else have their own tips and tricks that I can add to the list?

[jennifer]

    You can sand the area flatly lightly and randomly with 80 grit, just before you get to the mdf, sand the whole panel with 400 grit This time flat, random and fairly aggressive (cross hatch type patterns over large areas work best) , Now if your hole is down to the wood and still a problem, wipe some glaze putty across it with a razor blade, (glaze is like bondo, but more for final finish trouble/pinholes ) .... Sand lightly, prime and refinish.

[fanneyjack]

Bondo, spackel, silly putty, grape jelly,...anything but wood filler!

Bondo is the best. Good Luck!