Ok, kvetch says the best position to assume is the Relaxed Horny position, which I think just means whichever way both of you are comfortable. :)
Also, instead of going for "fabulous", I'd recommend going for "average", because "average" is infinitely more achievable, more realistic, and easier to aim for. Remember that the closeness you two share is already fabulous, so anything else is a bonus. :)
Now, for the story ...
A few years back, I had just had some really serious surgery (which I am still recovering from). I was in a lot of pain which made it very difficult for me to move, and for that I was on very strong opiate-based painkillers. One side effect of the painkillers was constipation, for which I was on other, different tablets. One side effect of the surgery was that I was strongly advised to avoid straining during bowel movements, otherwise I might rupture something.
So imagine this, I had a seriously bunged up poo factory and couldn't strain it out. What a dilemma!
The solution I was kind of forced into was, on the days that things just weren't going to move without intervention, I ended up soaping up my index finger and hooking out everything I could scoop up.
After a few times of doing that, I lost any apprehension whatsoever of poo and anus and rectum. It took no time at all to regard that activity as totally mundane and normal.
So if you tell that to your husband, and remind him that poo is only poo and it has been made you and him and everybody else, and it's a body secretion like saliva and ejaculate and urine and tears and sweat. Tell him how it can take a few times to get used to it, and once that happens, think of all the yumminess which can ensue. And how long did it take him to get used to and good at sexual activity? So, think of that.
There. Oh, almost forgot...
And they all lived happily ever after. With my poo. The end. :)