In the case of paint, water will not help, but there is another mechanical method. It consists in the use of a drill with a metal brush, and earlier used sandpaper, which took a lot of time.
Then you need to carefully examine the wall for the presence of irregularities, cracks, tubercles. The gaps are covered with plastering solution or installation foam is used, and the tubercles are removed using the same drill or hammer.
If the initial preparation of the surface is made, then it can already be primed. And then two layers of putty are applied. The wall will be completely ready after processing with sandpaper.
It is necessary to remember the main rule when applying putty – this is its overlap. The correctness of these actions consists of what hand you hold a spatula in, and then you should start.