What breed/type of sheep do you have? Fine wooled and medium wooled breeds only need to be sheared one time per year (usually in the spring so they have enough wool come winter). Long wooled breeds can be sheared once per year, but depending on where you live, they can/should be sheared 2x per year.
We have a professional shearer come out and do ours. She gets them done quickly & correctly so there's very little stress on the sheep compared to if we do it ourselves. She uses electric clippers (not sure what brand/type), but she sheared my old ewe at the fair during a shearing demonstration with hand shears.