We used to move our whole flock across the road and back. Once they'd done it once, they would just make a dash for the field they were going to and take seconds to cross. We have moved ewes and ewes with lambs that way.
We have four people, all wearing high viz vests, one on the road each side to stop any traffic, one in front with a bucket, and one behind in case of any which change their minds - which they don't.
Moving single tups is different - halter plus two people. When we bring several tups across at tupping time, we use the trailer, just to make sure we decant the right one into the right group of ewes.
Several farmers round here still drove their sheep across and along roads, even the main road, always with at least two people, usually more.
The very first time we moved the sheep across the road, we were nervous as you are, so we ran hurdles across the road, with the neighbours to stop any traffic, but the sheep could see the grass on the other side, much more exciting than a strip of tarmac, so we didn't bother with the hurdles next time.
Anyone who had to stop was always enchanted at the excited leaps and bounds - never had a complaint, or a shovey driver.
However, if you're nervous, use the trailer for safety until you are more confident.