for a really good finish, (and assuming you aren’t going to have blown plaster in which case a reskim might be a good idea),use two layers of the thinner lining paper. Do the first horizontally, the second vertically, so you don’t get overlaps.
Wallpeparing is actually relatively easy, take your time, use a decent quality paste (I used ready mixed tubs personally), and a sharp blade for cutting. Of course try and avoid bubbles but don’t fret too much on small ones, usually they will disappear as the paper dries and contracts slightly, stick a pin in the bubble to allow the air out as it does.