Someone on this site theorised that leaving small gaps in lining paper was the way to go and painting before filling would show up any areas requiring filling while also allowing you to see any edges which may have lifted to be gently glued back down. The fact that an edge may lift after filling (wet plaster) and painting could then prove more difficult to deal with.
Here's my experience so far...........
Daughter's flat (1950's ex council) consists of unpainted boarded walls and poorly jointed ceilings which were wallpapered
and after strippingl required lots of filling and sanding to get a reasonable surface for lining paper. First room walls came out good but you could see where improvement was required so a steep learning curve for my second room with lining paper, where I did the walls as well as the ceiling,
I took great care to ensure good paste cover to the edges of the 1400 lining paper, allowing it to soak for ten mimutes then instead of a wallpaper brush I used an old "Artex" caulking blade which gave a very flat finish indeed squeezing out any small air pockets, glue etc.
I also made a point of turning the lining paper round each corner about 50mm which gives a nice clean finish. Also means not having to worry about filling corners with easyfill or caulk (caulk gives a slightly different texture which shows through the finish)
Gave it a coat of white emulsion then after drying used a snap blade to tease out and fix a couple of loose edges.
Filled the gaps with Easyfill 20 and allowed to dry.
Sanded using fine sandpaper folded over once as I found this gave me a better feel for the light amount of sanding required rather than using a block. (Easyfill sands very easily unlike some surface fillers which dry rock hard and would need a block)
Ran a coat of emulsion down each join, making sure to avoid leaving a thick edge before leaving to dry then painting as normal with one more coat of emulsion.
I used coving for the ceiling so didn't have to worry about the joints up there.
Turned out very well indeed and my daughter was very pleased as opposed to her face when I was sanding it all down at the start...... messy
Now on the narrow hall where the ceiling was so bad it was easier to screw in a small frame and put up tapered edge plasterboard.
Only 2300mm at it's widest so no cut edge joints.
and it also proved a lot faster than scraping wallpaper, filling, sanding, papering etc, etc.
Quick fill of the tapered edge and light sanding and we're good to go with the coving.
Look, forget the force, use patience.