Dont worry..I'll answer your question...
Ok...first thing...do you have the receipt for the 'paint for new plaster'?...if so take it back and get a refund...all it is is contract (non vinyl) emulsion..the cheapest type of emulsion we use...its been put in a facny tin to rip people like yourself off.
Is the new plaster deep?,....i.e not skimmed..if so youll need to use contract emulsion, if its just a skim then you can use ordinary vinyl matt.
You should allow the walls to dry out though...this isnt DIY sos or 60 minute makeover!!!
In theory it might work..in practice, its dodgy and youll be the one left with the mess.
If you are going to use heaters in the room the walls may appear dry on the surface but may not be underneath so take away the heaters for a day first to see if any trapped moisture comes to the surface.
Dulux superflat...thin the first coat by a good 30%
Johnstones Cova plus and about 20%
Hope that helps