Filling screw holes in MDF cabinets

[Pigeonpost]

I am intending to repaint my kitchen units and also would like to replace the handles with single screw centred knobs. Two applications of Polyfilla and sanding with 120 paper has got me to this point which I do not consider to be good enough. Any advice please?

I can't see it clearly enough, but try wood filler instead. I've recently used one that comes in a little pot about four inches high and applied it on some fiddly bits and pieces using a small palette knife instead of a much larger filling knife. As the holes you are filling are right through the doors could you fill the holes with pieces of bamboo skewer (or matchstick or cocktail stick) glued in and then filled around at either end?