This won't work with most of the products we are talking about in this thread. Merino wool in manufactured clothing today is often either combined with synthetics or otherwise treated to prevent shrinking. Some go as far as needing a good drying in the clothes dryer to give back shape. In contrast, drying usually shrinks the heck out of wool (as does hot water). Smartwool socks fit in this category. The general rule is, if the washing instructions say you can wash and dry them, they won't shrink/felt.

Not all wool, however, is like this. For example, I have some old red Wigwam 100% wool socks that only get a cold water wash and are line-dried. I also have an old ragwool sweater that I can wash but not dry--even though it's 85% wool, 15% nylon.