Are Castlemilks a roo'ing breed? Roo'ing is the correct term - plucking sounds rather painful

I thought the main roo'ers were Shetland and Soay, occasionally Hebs.
They are ready to roo when you can clearly see the 'rise' about an inch above the skin - a clear horizontal line in the fleece with the new-grown wool coming through from the skin, the old on top. The idea is to separate the fibres at that point, not to pull all the fleece off to skin. It's the same line you would hand shear through.
The first time a sheep is roo'd it will likely hate it, but they do get used to it.
You need to tie your sheep to something, either with a halter or in a headstock (the latter if they're jumpy).
Working in the hot sun is best, as the new and old fibres will slide easily over each other.
Sit on a low stool (milking stool ideal) and start at the neck, where the wool tends to come away first. Take a small lock of fleece in one hand, brace the skin with the other. Pull and wriggle the lock - if it comes away easily, it's ready, if not, leave it another week. If only bare skin is left, you're too early.
Take your time, as rushing will hurt the animal.
If you intend to use or sell the fleece for spinning, you can sort as you go - one container for dags and skirtings, another for useable, clean tufts of fibre.
Gradually work your way down one side. Usually the britch will be ready a couple of weeks after the rest, as Marches Farmer says, so you're left with pantaloons for those couple of weeks.
If you and the sheep are restless, do one side one day and the other the next. Otherwise, retie when you've done as much on one side as possible.
There is a terrible American You Tube clip, supposedly showing how to roo. Please please don't do it that way - she's not gentle.
Sometimes with Soay you can 'unpeel' the fleece and remove it in one go - it's a bit like skinning a dead animal, but obviously in this case the animal is living.
Equally, once you get to the same stage as when the sheep is ready to roo, it is also ready to hand shear. You can do this using all the proper shearing positions, but I know many people who do them standing up, even one person who uses dressmaking scissors. You need to be extra careful not to nick skin folds, but it's perfectly possible, especially when you don't have enough sheep to warrant waiting for a shearer.