Dupont URO is easy to work with. I used it to level some pitted sheet metal and it covered quick and sanded easy.
In a Dupont training manual from a while ago they talk of thinning the URO down to be used as a sealer coat. It is mentioned that it is a better sealer than some of the sealers.
I found the URO works better if you add in more thinner than recommended. I found the old ratios and found it much easier to work with.
The URO sands well dry with 360 dry paper for final sanding (final grit depends on top coat).