@ProV1: I would love to try it with a woman's fist.... I would love to try it and see what it feels like to have a fist spinning around in my rectum massaging my prostate. I would imagine the sensations would be unbelievable.
ProV1, you're right. It feels wonderful. My wife fists me. Here are some images: https://www.zity.biz/index.php?mx=gallery;ox=showalbum;ax=7712
Pam has a large hand for a woman, only slightly smaller than my hand. (Her brother played linebacker for LSU and has huge hands.) The largest diameter butt plug I can handle is about 3 inches. If you could work up to this diameter, Pam could fist you. 2.75 inches might be enough. 2.5 inches might be enough for a small female hand.
Buttwoman's most recent blog page provide an excellent how-to guide for the first fisting of an anal fisting virgin. See: https://www.zity.biz/index.php?mx=blog;ox=showpage;pg=4283 . It's also a very HOT read !
The hand position for fisting, the 'duck bill', is to put all four finger tips as close together as possible and press the thumb into the hand and fingers. Right now, your wife could certainly push in her duck-billed hand so all four fingers and her thumb are an inch or two inside you. You might want to ask your wife to generously lube you and herself with silicone lube, push her duck-billed hand slightly inside you, and just hold it there so you push back against her.
Relaxing your anus for fisting is very important. Buttwoman says having anal sex first works for her. I'm sure having your wife fuck you almost to orgasm with a 2.5" dildo would relax your anus pretty well. The method I like is to take several hot, gallon enemas, do a thorough 15-minute expulsion with tummy massage and pressure, and plug with my favorite 3-incher for an hour. I'm clean and dry when I pull the plug out, and totally ready for Pam to fist me.