You know, there is a video of a guy who claims he is an expert at picking up women. I'm sure if you say a video of his front door he would have women coming in and out frequently. What you don't see is the tons of women he has approached and the amount of rejection he has faced to achieve this.

I think control in lucid dreaming is similar. You have to try and try again. I have had many lucid dreams where I try to imagin pulling $1,000 out of my pocket. Instead, I end up pulling out $100 or something like that. I think there is something in your dream or brain that sometimes prevents you from getting exactly what you want - something that wants to say "I stilll have the control."

Anyways, I think this is definitely a skill that can be mastered but it will never work all of the time. If you have any control over your environment you are either really talented or have "tricked" yourself into getting what you want.