Thanks BigLeegr. My understanding is that another reason for the wipedown is to check one's progress after a pass has been completed - the idea is to remove as much of the residue as possible, to ensure that the residue is not acting as a "filler", and hiding the marring. Can I assume that plain water is good enough for this purpose?
I'm a newbie at this - I had a brief attempt some time ago with a random orbital, and didn't have very good results. I have a rotary now, and it's WORKING. Hooray.

(I don't think I was working the polishes for long enough with the random). Even SSR 2.5 by itself is producing a very good finish indeed. I am practising on a black bonnet lid from the wreckers. I am very encouraged.
Greg.