Advice on filling

On what material?

 

Have you sorted out the condensation?

 

It's a horrible job, Timberr - soul destroying... The 'edge' isn't thick enough to take normal filler, but still a pita to sand.

Is the remaining paint very secure, or is it the situation where you can chip and scrape away the paint edge almost forever?

Assuming the rest of the paint is well stuck, what I tend to do in these hellish situations is to use a sanding block and 180 grit to just remove any raised edges from the broken paint edges, and try and ease off the surrounding paint edges to some extent. Don't bother trying to feather the edges down - if you try and do that, you will almost certainly sand into the surface below too, so you'll have worn grooves in the plaster just beyond the paint edges...

Then I roll on a couple of thick coats of orn'ary matt emulsion.

The paint will (a) 'balance out' the wall surface so's it all behaves the same, (b) helps to seal the paint edges and (c) let's you know chust how bad the wall is - it might not be as bad as you feared.

Finally, you can get some ready-mixed p'board jointing filler and a large flat rubber blade 'trowel' - they're normally used to fill the tapered edges of p'board sheets. This stuff will dry quickly, sand easily, and is very fine.

Apply, dry and sand.

When you think it's all brill, roll on another coat of white matt, 'cos there's a chance that the paint will raise the filled areas a fraction so's you can chust see them again. If so, a very light sanding will sort it - then you are ready for your proper top coat.

If you are in areas prone to condensation problems, use bathroom/kitchen paint or 'silk' (yuch...)