Diamond satinwood over vinyl matt on wooden furniture?

Hi, with mdf you are better of sanding down and starting fresh making sure you put at least 2 coats of under coat on first before satinwood.

Hi the MDF need good sanding and clean as well, make it to look fresh You have to use universal prime or undercoat before you apply the top coats Otherwise after couple of week the paint it will come off,or you will not have good finish

Hi, I would advise to sand down slightly, apply 1 coat of undercoat (well brushed or well rolled) depending on preference and after 1 coat of diamond satin wood. It would be ideal to add a tiny bit of white spirit in your satin wood as it gonna make it more workable a give a smooth finish.( if You don’t you might get a lumpy finish) Remember that the undercoat will be your main base and any imperfections will still show through satin wood so make sure to apply it nicely.

Sand it all down with a fine grate off sand paper or a sanding pad works really well to not scratch the surface to much then apply an appropriate primer and build your satin finish on top off primer definitely don't just apply satin ontop of matt finish .

The most important factor to successful painting is good keying of surfaces. The microscopic scratches afforded by rubbing down allows the new paint to flow into the existing paint surface. Provided that the previous paint is well adhered to the substrate. I would advise if its feasible to remove as much of the emulsion as possible (emulsion by definition is a brittle paint and will be subject to chipping ) the seal with Zinsser BIN primer. Then complete with your desired finish. I hope this helps . Good luck