Fascinating - I've never seen Milliput go like that before! Or not..... still, as you say, not a disaster.
Regards the paintwork, there are no short cuts to actually using a pad of 2000 grit wet-and-dry and dry to achieving the effect. I know some people just Polish instead, but that doesn't do the same thing.
I agree entirely about the Unimat 3 - I have one, and it's such a useful little machine (I remotored mine with sheep-sheering motors adapted with variable speed, which have been brilliant over the years. They run cool, are more powerful, and by adding a pot, give me variable speed)