Here it is important to clean the wall well before attempting to overcoat with fresh paint.This cleaning is best done with a high pressure water washing system.
Using high pressure water/ air combination is usually good enough to remove all dirt and loose or flaking paint, including possible chalking of underlying degraded primers or paint coats.
Allow the wall to dry out for at least one (sunshiny) day before painting.
It is possible that after drying there appears to be some flaking or delaminating of the free edges of old paint work. These areas should be scraped with scrapers and sandpaper until only very well bonded paint is remaining on the wall.
If paint was removed in this process to expose clean/raw plaster, then follow the previous blog post recommendations with regard to priming new/raw plaster work in these areas.
At this stage the ‘mapping’ which may have resulted from the above preperation work may need to be addressed with suitable fillers and filler mixes as detailed in the previous blog post ‘painting of newly plastered walls’.
Painting in the colour of your choice can then proceed. Application of two coats is recommended.