Firstly, you need to know that wool garments do NOT need to be washed often. Hang them outside or beside an open window for a few hours after wearing – that’s all that’s needed mostly. Really: wool wicks off sweat and kills the BO bugs. Soiling can be scraped off carefully when dry, then shake out the garment and put it straight back on. For those particularly nasty stains, like red wine or tomato sauce, most can be soaked off on a very soapy solution followed if necessary with a rinse in a white vinegar solution. If any staining remains, you can reduce its visibility by gently plucking out some of the stained fibres. Never, ever use bleach on wool: it causes wool to melt and disappear.
So. Given that you only need to clean that pure wool suit or sweater every other month, you could consider getting it professionally cleaned. If, like me, even this small splurge sets your Scottish ancestors birling out of their graves to wail and groan at you of a night, you can hand-wash it on cool-ish water with a suitable wool washing agent (okay, okay Great-uncle Hamish, back in your box) or the cheapskate option, shampoo – for dry hair if possible. If your deceased Irish granny is giving you nocturnal earache about how she didn’t work three jobs to scrimp and save so that her grandchildren could wash their clothes by hand, you could use the wool programme on your washing machine. Again: really. Mine have survived front-loaders and top-loaders.
Then, the issue is the drying thereof. Unless the wool is “superwash” – it should say on the label – no tumble driers. Instead, roll the garment in a bath towel and squeeze, don’t wring the excess water out. Lay it out flat and pulled into shape and leave it somewhere airy and/or warm (but not in direct sunlight, or close to a heat source).