I think he'd freak if I used a hair dryer, he currently needs sedating to be clipped (however this is work in progress - I am trying to get him used to clippers lol) but the hair dryer thing is actually a really good idea haha If he would let me. I might try!
I make a bucket of warm water and use a flannel to dampen the mane in sections. I put very small amounts of shampoo on the flannel and rub into the mane. Use the least amount of shampoo you can get away with, building it up slowly, as the more you use the more you have to rinse out. To rinse, i squeeze a wet flannel around sections of the mane, holding the mane away from the neck so it doesn't get to wet. I just keep doing this until i can feel all the shampoos gone.
Next time i'm going to try using a small bucket to dip the mane into, and see if that speeds up the rinsing (my mares mane is very long.)
Looking forward to hearing how other people go about this.