In this situation, if

You also do not need to get carried away too — there is a risk of soaking the wall strongly — the putty layer can be broken, or the plaster will deteriorate. Old wallpapers should swell — they will begin to drop from the walls, we begin to dismantle them. A spatula will help — just an indispensable tool in this situation, if it is not — the most ordinary scraper is suitable.