How should I tell my wife that I want to have her use a strap on?

Great advice! I need to save up for a nice Feeldoe! They look like fun!

We finally tried it - my wife was amused but not interested in repeating it. One-and-done for us.

To clarify my earlier post, I just meant clean. That varies in how far you actually take it, but the most important part is the peace of mind you can give her that she's not going to run into anything during the act. The minimum I always do is make sure to go to the bathroom at least an hour or two before, check it with a gloved finger, and then finally wash off the exterior.

You can use something like the Colt Anal Douche to make sure it's clean if you're not sure, but she might be even more grossed out by that thought than the actual pegging, so consider that. Shaving also usually a nice touch.

Again, the most important thing is just make sure it's clean enough for her. How clean that is varies, but do what you have to. Also, I second the other advice given here too!

If she enjoys receiving anal sex, bring up that you would like to experience the feeling she gets, both the positive & negative. I now understand when my girlfriend doesn't orgasm how she still enjoys sex. As well as the different levels one can get to by changing the rythm, the thrusts, how enjoyable it is to her when the tip of my penis is barely in her, & taking it out & putting it in. It has helped me understand how to satisfy her a lot more.
Also she understands it isn't easy being the guy thrusting & knowing when to change things up.

You're lucky she even uses a finder during a handjob. The fact you're even that far is only a small step to upgrade to pegging. I had my wife giving me a handjob one night while using a vibrator on my balls and I spread my legs and asked her to roll the vib under my balls. She did. After a few minutes I asked her to go lower towards my taint and she said "NO, I'm not going anywhere near your butt!". Yeah, just like that. I didn't even go there and she jumped right to it and shot me down.

I think that using a toy is much less intimidating than using a finger. if there is an ick factor you are a step removed. Just be open and honest. Be sure to mention that you respect her boundaries if she is really uncomfortable, but that you would like to try it if she would be open to trying it.

Degrees of approximation. Get her comfortable with her fingers and tongue first, play it up, let her know how amazing she is and how great it feels. How she knows how to please you like non other. Slowly work your way up from there, prostate toys, plugs, nonrealistic dils.. ect..