2009 Kubota RTV 900, 2009 Kubota B26 TLB & 2010 model LS P7010
In addition to reducing throttle you can also finesse of some call it to feather the controls (just gently engage rather than pulling fully open). Smoothly operating a backhoe is the mark of a skillful operator.
I normally run my B26 around 1800 RPM which provides enough speed but also reduces engine noise considerably. If I really need to slowly move in on an object (like next to a building) I may even reduce throttle to idle. You will have the same power just not as much speed.
Low rpm and experience will accomplish the desired result. All machines seem to respond differently, as well. I can't necessarily run your backhoe as smoothly as I run my excavator. I would have to get the feel of the machine which comes with time.
I've also found that practice without pressure improves smoothness. In other words, digging right up next to the house can make a person nervous and cause poor results. Get more familiar out in an open field where making a mistake has less dire consequences. Then try the close quarters work when it feels right. Not making any negative comments toward your skill or experience - just sharing info from my own learning curve (which is still underway and hopefully always will be).
The Ober book suggests moving water (like from a pond to a bank) to develop smoothness.
In reality, I dig a lot of stumps as I work, and I find I am usually RPM'ing way too high; as the machine will easily go into bypass whine.