and I suspect there are many different ways to do this, but I use short 6-inch "ball-bungies". They don't mar the boom, leave no residue to be cleaned up later,are easy to keep wrapped around the boom when not in use, don't bang the boom if wrapped enough times to be snug, and allow the cable to be slid or otherwise easily moved. if the boom is narrow, just wrap the bungies around it more than once. I also use at least one on each cable just for transport. That way, when I use a cable, I always have at least that one to use for securing the cable to whatever.
After wrapping a cable around your boom you can use velcro rip ties if you must. They are used all over the place. For hanging things from your Petrol bag you can use a variation on the rip tie, called a "piggin' strip". I switched to internally cabled boom poles a few years ago.