Personally speaking, I've found you can do it one of two ways.
Either you can try and roleplay the whole polite BS to try and fit in with the group.
Or, you can take advantage of your gaijin status and not deal with it.
Personally I prefer the latter since it allows me to cut through a lot of red tape when dealing with elders. If they get pissed, blame it on your foreigness.
Above all, I wouldn't hesitate to shop around for teachers.
So what if you piss some people off?
If something that minor is going to keep them from teaching you, would you really want to be their student?
In that case you should ask yourself, do they really have something worth teaching?
Japanese people are like any other people. Many of them like to take advantage of the fact that foreigners feel the need to be excessively polite around them, especially if they hold any sort of rank or status, even if they don't have the skill to back it up.
I've found the best and most skilled teachers in any culture are the ones that choose not to provide a clear seperation between the trappings of culture and what they teach.