You shouldn't have to ask, however, you should do the same for her, she shouldn't have to ask either, you should give to her as much as she gives to you. If you want a hand job just because you need to give it to her just because. It should be equal not just one sided, meaning you getting it all and you never giving to her. Making her feel wanted and desired will go a long way, and you can do that by starting it, initiate it with her dont expect her to initiate it every time, but she will be more willing to just do it for you if she feels wanted etc but you have to give too, without being asked. Give and take