Controlled shrinking of Shetland and Lamb's Wool sweater?

I have a few Shetland and Lamb's Wool sweaters that are mediums. However, I seem to really need a Small - Medium. If I spray the sweaters until only slightly damp and toss into the dryer, and check frequently for size, can I control the shrinking or am I risking ruining them?

Are there better methods to perform the controlled shrinking?

Thanks as always!

Controlled shrinking of Shetland and Lamb's Wool sweater?