I braid and tuck in a hair net
I make a two stranded cinnamon flat bun (ballerina bun) and add a can of hairspray ( not joking )
My hair is extremely thick and won't fit in my helmet without hurting, so I cheat and have it French braided then I either tuck it under my jacket or ill fold it and put it in one of those small hairnets at the base of my neck.
I put my hair in a ponytail and then put the tube hair net around it and fold it up in my helmet.