I just ran across this thread. I planted a Pinus densiflora Umbraculifera many years ago. It was just a foot tall when planted about 30 years ago. It remains one of my favorite trees - its star feature being the flaking red bark Lucy mentioned above. Its bark starts flaking at a young age. I was trying to find some old pictures to show its progression but the earliest I can find shows its trunk at around 15 years of age. You can see it is already distinctive.
Here are a couple of pictures from about 10 years ago. I don't have any more recent.
I didn't do much pruning on mine - I removed a few inner stems but it naturally formed multiple trunks. Yours will likely remain smaller than mine, since it is Umbraculifera Compacta, but it should still have the same beautiful bark. I would definitely agree with opening it up to isolate a few primary branches and show the bark character.
The only other advice I have is to anticipate that it get bigger, despite the 'Compacta' name. In my original planting, I had the cutest assortment of dwarf conifers imaginable - the Tanyosho pine was surrounded by other 'dwarfs' including Pinus parviflora Hagoromo, Pinus thunbergia Thunderhead, Cedrus atlantica Sargentii, Cedrus atlantica Uwe, Picea orientalis Bergman's Gem, Pinus strobus Greg, Tsuga canadensis Pendula. 30 years later, Tanyosho and Thunderhead are too tall to candle prune anymore. Hagoromo, Uwe, Greg and Bergman's Gem all died after being shaded out. The Sargent cedar and weeping hemlock are doing fine, but they are way too crowded near the surviving Tanyosho and Thunderhead.... You live, you learn!
