At bloody last, I figured out the white forelock trick. For anyone who wants to know, create/get the base image, set it as a starter image, then go to 'start image settings' and block out the part you specifically want your prompt to apply to.
I also owe a significant debt to
@Ellie_Valkyrie, because this started many, many generations ago as one of her works because I couldn't find anything else with black and white hair.