assuming it doesn’t override consent requirements (Eg : if she wouldn’t usually say yes to anal, she still won’t say yes to anal), mouth; since it’s the one that will be agreed on the most.
assuming for some reason, the lady will consent to it each time, anal.
I’m usually pro porn , pro masturbation, but this is the one time that it might be helpful , since you stay horny/pent up to actually perform more to the way you want to during sex.
Just don’t take it too far.