There's no shame in just paying to have a sedated sheath cleaning from a vet once in a while.
Personally, I don't wash my boys' "areas"...ever. I DO think there's a natural blance of healthy oils/bacteria in there, just like women shouldn't douche,.....HOWEVER, yes, that doesn't stop a bean from forming because geldings are unnatural creatures (the life of a stallion would help clean his penis from frequent erections, matinge, etc. Plus geldings tend to not drop all the way to urinate and little dribbles cling to the end, attracting more dirt than normal.
I still don't soap them up. I pick off any obvious loose flakes of skin, if I notice them "dropped" and relaxed while I'm grooming them. I do it so fast they either don't notice, or don't care. Sometimes they get erections (all male horses do on occasion) and I take advantage and quickly check for/pick out any beans about once a month or so. Doing it more frequently keeps them to a minimum, and before they are large enough to be an issue. If I'm hosing off a sweaty horse, I might shoot some water up in there to rinse, but that's it in the way of cleaning.
I've NEVER had one develop problems from doing it this way-no infections, no swelling, no irritiablity. Toby has a really greasy smegma that's very tarry and smelly, but some horses have very little. He also ENJOYS any digging I do. :roll:
If your horse has never been checked for beans, then yes, a good cleaning to check for beans by a vet if you are inexperienced is a good idea, then maintain regularly with the "quick pick". The "quick pick" is also a good way to desensitize them. It's over before they react, you catch it while they are already relaxed and it's not as invasive. If you have a horse that wants to kick, go ahead and have him professionally cleaned. If it's a really big bean, sedation might be the safest route, then when he's comfortable again, you can work on training him to let you touch it.
To desensitize, I just run my hand lightly along the belly (standing out of kick range) and over his sheath. At first, I do it once or twice if they are antsy. Then come back to it later. If you are quick, you will have touched and quit before he can react and he will quit objecting. Do it every day. Then start to let your hand linger longer over the area. Eventually work up to being able to stick your hand in his sheath and pick/rub gunk from the entrance-almost ALL horses I've done this to actually start to drop at this. Keep picking gunk everyday, let him relax, and quit. Work up to grasping his penis..then eventually do a quick check of the end. Taaa Daaa! You've just checked him for beans.