Photo by Holly Rowland.
Clothing weblog Put This On recommends this simple, but not-so-obvious solution to low-quality wool garments:
Fill a basin with cold water and thoroughly soak the garment in it. Then drain the basin and gently press the water out (woolens should never be wrung). While it’s still damp, apply a liberal amount of hair conditioner and work it through the fibres. Higher quality hair conditioners will work better (I recommend Bumble and Bumble*), and make sure you’re not using one of those 2-in-1 “shampoos and conditioners” mixes.
After working the conditioner in and leaving it for a half hour or an hour, you can lay it out flat to dry and it should be noticeably softer. Hit the link for the full set of instructions.
How to Soften Wool [Put This On]