Hi Argus, you could try either of the answers you have received as they should both work. Just make sure you have removed all the paste from the wallpaper as any left could ruin the finish. I would also say that if as you say, you are going to use a vinyl silk finish then make sure that the walls are as flat and free from blemishes as possible. Any little marks will show through a silk finish and stand out. Good luck with it. Shed.
personally i'd be very reluctant to use any kind of sealer. removing all traces of old wallpaper adhesive is a long, laborious and difficult job. if you leave even a small trace your paint is going to peel. no such problems if you line the walls first.