I use hotwater and Dish soap.,.. after I soak them in a water bath for a while.
I also decided to just skip the dang haki brush and bought myself a high quality watercolor wash brush instead. The one I chose was the Da Vinci #60. ( about 2 inches wide) which at $60 US on sale,. was a high initial cost but it never looses any bristles. I bought it in June and it is really still in excellent shape. I care for it religiously(granddaughter of a signpainter, Brushes are sacred items in themselves)
I figure I was going through a Haki brush a week. more with sponge brushes and with the cost of gas to go and get new brushes and the cost of the brushes. I'm probably on the cost effective side by now.
I do like the beauty in which a wash brush holds the gelatine size. I get great coverage but not puddling.
So I went ahead and purchased another to apply gum with and have not been disappointed at all.
For smaller prints, 4 inches in width, I ve been using a great little watercolor wash brush I found along side the road. Windsor Newton 995 series. I love the way it holds plenty of gum and washes out so nicely.
All that being said. looks like I'm going to get great UV today and I'd better get cracking!