I need to 'skim' a (emulsion) painted wall.

By skim I mean a coat about 5mm thick  (to bring it flush
with the adjacent part of the same wall which has been
previously skimmed (I removed some shelving which
revealed the unskimmed wall).  Its not big - about a
metre wide.

So here are the questions:

- is it ok to pva the wall prior to plastering or do I need
any more radical prep to key the wall?
- I'm not sure if this is too thick a coat just to skim with
multi finish (2 or more coats?)
- or if I would be better off using a base coat (bonding?)
+ finish,  or use 'one coat plaster'?

Cheers!