It is plastered walls. (1913 house) I am in process of stripping 96 years of painted wallpaper, lol, about 3/4 done. But I had just finished the DR and had problems getting the paint on walls with 3/8 sleeve. Was using Purdy WHite Dove 3/8". Was advised to go to 1/2" to hold more paint as the walls are 10-12ft high. Guess I just didn't realize they make the sleeves for smooth and semi-smooth. That being said, is it okay to use the semi-smooth for flat paint sleeve on a plastered wall with satin paint?