Hubby and I went on a hand shearing course last weekend (we have four Jacob ewes) so here's my experience!
Its physically hard work on your back, and we found it a two man job. Once you have the ewe positioned on her hip she is usually pretty calm, but if you make a mistake and let her feet hit the ground she struggles and you need another person to catch the ewe or take the shears off you quick so you can grab and re-position. Also, because we're beginners, we did it 'tag team' when we got knackered!
There is a right way of doing it. If you don't care how the fleece ends up, you can probably clip it off any old way, but we were under instruction and still ended up with a sack of bits all over the place. There is a proper order of doing it, and the correct way to position the sheep for each stage which makes it quick and relatively painless for the sheep, and less hard work for you.
You need really sharp shears or it takes ages. After reading on here, I got a pair of Jakoti shears which were new and razor sharp and really did the business. My hand didn't ache after four hours shearing.
Most important thing to remember is to pull the skin tight to avoid cutting the skin, and never pull the wool. The skin tents and you can easily clip a slice in it.
We were working on mule ewes. They were mostly very obliging. Our four jacobs are a different kettle of fish and we won't be hand shearing them - they fight like crazy! So my parting shot is, let someone else do it! The course was great and if you can find one next year it's well worth going on, just for the handling experience. If I was forced to shear one of my sheep, I would do it with the sheep standing up as much as possible, tied to a fence, and not care what they looked like afterwards!
Best of luck