In your posting Franksjewel, you have hit on 3 of My personal fantasies in one paragraph. First, and easiest, to offer your slave body to your Master or Owner for pain and marking, taking the inititive to let Him know that you want to be used like that and what to wear His marks.
Secondly, to rim His ass hole. It is such a very personal and intimate service, not often provided by subs. But again, you don't wait to be asked by offer such service even tho it is degrading to be an ass licker. But it does provide such exquisite pleasure to your Master and I'm sure He appreciates it and sleeps well.
Finally, the very practical service of being a living and personal urinal. It would be wonderful to just call over One's sub and say "I need to piss" and have her take care of it so completely. After having My cock served in such a useful way, I might even reward the slut's mouth with a growing and horney cock, also providing her with another reward, a nice mouth fucking and some precious cum for her to also swallow.
Keep up the great work and Frank is a most lucky Man to have your dedicated service.