Size or mist coat freshly skimmed wall?

If I am wallpapering on fresh plaster I personally do both, I mistcoat and I size the walls, even doing both things you will still find your paper wants to stick to the walls very fast. I always use Hamilton perfection roller medium pile. (Green)

dyer spot on dont paint just size pva if papering

It is best to size a wall on a freshly skimmed wall Putting paste directly on a wall allows the wallpaper to move more freely when you're positioning it into place. The best roller to use for a top finish will be a smooth to medium pile roller sleeve.

Personally I would use a Plaster sealer such as Zinsser Gardz in this situation. If you later decide to remove the wallpaper any residual paste can then be washed off easily. And you shouldn’t rely on any wall coating to kill suction, walls should always be cross lined for this reason prior to wallpapering, this will stop the wallpaper drying too fast and all the joints pulling open as it shrinks.

37+yrs in the trade. I agree with "A lick of paint", except I always mist coat fresh plaster whether it's being papered or painted as it reveals any imperfections that can be filled and rubbed down (I know many will say that the paper will cover any imperfection, but I prefer to have the best surface possible), then size the wall before papering. As for a roller, I use Wooster Pro Doo-Z Roller Sleeves, never had an issue with the finish on a properly prepared wall. Preparation, preparation, preparation every time, on all surfaces. Hope that helps.

Personally I would recommend that you rub down, fill, prepare and size walls then hang lining paper before you hang finished paper or paint finish. Thanks W.