When skiming old plaster, make sure there are no nails, tacks, blue-tack,
clumps of wallpaper or any other 'bits' on the wall, if there are, remove
them prior to applying PVA.
Apply PVA generously, don't skimp and give it two coats if possible, the
second after the first has dried....it doesn't matter whether you skim over
the pva dry or wet, but any patches not treated with pva will dry almost
immediately and make a bollocks of the trowelling-up process.
To do a long wall, start at one end (point 1) with stepladders and apply a
band across the top of the wall about 2 -3 feet down from the ceiling, all
the way from one end to the other.
Get down, remove steps out of area and apply another band the same width in
the middle of the wall, then, apply the last band whilst you are kneeling
down, don't be tempted to drop back onto what's already covered.
Once the full wall is covered in plaster, start again where you started
originally (point 1) and apply a thin 2nd coat, taking out most of the
imperfetions, don't be too picky, this is still only an initial phase.
Follow the same route over the wall as you did with the 1st coat, until it's
had a 2nd coat and is looking fairly flattish.
Wash implements, hawk, trowels, mixers and buckets.
Start again at point 1 and go over the entire wall with a light splash of
water over about a square metre at a time and take out any imperfections,
repeat this process until you are happy with the finish.
If at any time you are putting more marks in than you are taking out, stop
and wait for 5 minutes to allow the plaster to go off slightly then have
another go, starting from point 1 again.