The downside is that wool a bit tricky to wash (mostly hand-wash, or washed separately in a specific wool cycle). Or is there any methods you recommend to easily wash wool garments?

I have a merino base layer for outdoor activities and its care guide advises the use of regular detergent and a normal wash cycle: http://www.icebreaker.com/en/customer-service/product-inform...

Most modern sport-oriented wool (using merino) these days can be machine washed. So just wash them in a different load using wool detergent (Eucalan, Kookaburra, Nikwax), and lay flattish to dry. Use a garment bag if you have a top-loader with an agitator.

Put it in the freezer or outdoors (if you live in a cold environment). Not sure if this is actually a thing or just some old urban myth, but it's what I do. Maybe I smell though.

Even just outdoors in the sun: reduced moisture and UV will kill a huge portion of the population. Freezer kills because it's dehydrating, but for wool it'll also kill moth eggs.

Out in the sun works for the reason you said (UV).

Short term freezing isn't very effective as a way to kill bacteria. Once the garment is made warm again, the bacteria wakes up and the stink returns.