By hand held shears do you mean clippers with an integral battery or hand shears (like the Romans used)?
If you want to try the hand shears, Shetlands are the ideal breed to start with. They have a clear rise in the fleece and you just cut along that. If you wait for the rise to be about an inch above the skin, you won't cut the sheep. You will soon gain confidence and the blade zooms along. When you are using hand shears, you can feel the greater resistance of flesh compared with wool so you simply don't close the shears if it feels wrong. Also you only cut where you can see what you are cutting, except opening up the neck, but you would lead the shears with your hand then so you would cut yourself rather than the sheep.
With Shetlands you could also roo them, but that is best left until their second shearing, as the rise is more clearly defined than a yearling fleece.
I think the key to shearing sheep is to control them properly so they don't squirm and fight, and leave you to concentrate on the shearing. There are little tricks to keep them still in the various positions, which is a reason to watch professionals and see how they manage. For example, when they are on their sides, a foot under the shoulder makes them think they are stuck so they don't try to get up, and when they are on their bums for clearing the belly, a hand pushing down on the brisket can settle them.
I haven't looked but there should be Utube clips for both machine clipping and hand shearing. If you can find some then watch those many times to memorise the patterns. It's also a good idea to see shearing demos at shows, and even shearing competitions, although they shear for speed more than beauty at a competition