hi, obv if your going to use anal masturbation you cant just wack in ya fingers, weher you ment to aim for ? dunno if i like the idea but im curious !!
'the zone' ?
You're "looking" for the prostate. This is a walunt sized structure that is just under the base of your penis. So insert your finger and then move towards the front of your anus and just under the base of your penis. You'll know when you're there, you'll feel your penis sorta respond. Massage that area and you'll discover what anal masturbation is all about.
Actually, some people don't get that much pleasure from stimulating their prostate, me being one of them. I actually prefer rubbing/fingering the anus itself while jacking off, as the feeling is much more pleasurable.