The best way to polish walls
1, first of all to be able to flatness as the preferred goal, wall sanding more 240, 320 sandpaper first test, if sanding up is not very strenuous, can do the flatness is very good, then continue; if feel sanding is very strenuous, then switch to use a low number of coarse sandpaper and then test. If you use coarse sandpaper for the first time, you will need to sand again with fine sandpaper to eliminate the scratches left by the coarse sandpaper and to make the wall more detailed.
2. By putty quality. Non-water resistant putties are easier to sand due to their loose surface structure and are usually sanded with 240, 320 or higher grit sandpaper. However, as most non-water resistant putties are of poor quality and the powder itself is generally of a low mesh, it is difficult to achieve a very fine finish even with high purpose sandpaper. Water resistant putties have a relatively strong surface structure and are much more laborious to sand than non-water resistant putties, especially some high strength water resistant putties, so it is difficult to wait until the putty is completely dry before sanding.