To be honest, I'm not an expert on blocking by any means. I've blocked sweaters on a wooly board, I wet blocked a scarf recently and that came out nice. I don't think I'd block hat myself, but then again, I'm lazy that way. I would certainly give in a go. I think I'd wash it in warm water--very gently--just kind of press it around with an iota of wool wash. Squeeze the water out in a towel and then if you have something to shape it on, I'd think that would be best. Since most of us don't have head mannequins, I've often thought a balloon would do in a pinch. Or maybe if you just shape in flat until it's dry, it'll get it's poof back.
"Trust the pattern!"
Time flies like an arrow, but fruit flies like a banana.
Hop aboard while we follow the cloud-covered van of knitting harmony, man!! Woooo!! --Hedgehog
IngridKH on Ravelry