Wallpapering

Just bought some pre-pasted wallpaper but have a couple of questions about preparing the wall surface before I start papering.
I've had to use a fair amount of Selleys Spackfilla to cover some cracks and irregularities in the wall. The dry Spackfilla looks fairly absorbant - will one application of wallpaper size over the Spackfilla be enough before I start papering?
And is it good practice to apply additional wallpaper glue to the paper or is the pre-pasted wallpaper generally good enough to stick OK?

cheers

Tim

paint a sealer of the filler spots...as plaster and other fillers are porous . or the glue from the wallpaper will soak in, "dry spots" i have never had to size with pre-glued wallpaper, just don't let it soak , pass it through the water slowly so all the paper gets wet