I think you can get by with machine washing these days with the modern front loading machines with no agitator like the old top loaders had. The agitator was the shrinkage culprit I think. The modern machines have a, " Hand Wash " setting and this is what I use when I wash my Ullfrotte' long johns. Most of the newer modern dryers are the same... they have a very low heat setting or air dry setting so you do not overheat the wool and shrink it. If I have the time I simply lay mine out to dry outside.
I try not to wash my heavy expensive outer layers if at all possible. I hang them out the entire season from Oct to Jan on a clothesline.