I wouldnt PVA, just do a thin waterdown coat (miscoat), then roll as normal, unless you have to fill any indents gouges etc, but you can find the info on that on the link for the post Wolf mentioned.
As for the metal bits, I must admit I have done it both ways, I have U/C then emulsioned, only if I have a bit of time and have something else to do while waiting for the U/C to dry, if not, whack on a couple coats of the colour to the edges prior to actually rolling.
They do take more coats to cover with the emulsion.