Leonard, I think that's a pretty decent way to break in an engine. The fact is, a Bullet will go somewhat faster than 30 mph at 1/4 throttle. Also the idea of varying the engine speed is a solid approach.
I haven't been too concerned with sticking to hard and fast guideline for break in as the bike hasn't been ridden in temperatures over 40 degrees F. For me, heat is the enemy. Heat is what destroys machined surfaces and seizes pistons. I've been doing lots of short rides, getting the engine up to temperature, then parking it for a while. It's been that way for the whole first 240 miles. I use whatever throttle position I care to up to 1/2 throttle. The 1/2 throttle position is only for short bursts. The bike performs well under these conditions.
So far my engine doesn't use any oil, has good plug color and is still using the plug that came in the bike when new. A spark plug should last thousands of miles. If someone is getting oil fouling, it's probably because of running too slow and lugging the engine.