reallocating thief skills by training

[Bolo]

Someone mentioned that it's possible to reallocate thief skill percentages by training. How does this work?

Are there limits on how many percentage points can be shifted into or out of a given skill? (If not, this would be an end run around the restrictions on how each level's increment can be allocated.)

Is self-training sufficient? I think it should be, but if it's not, does the instructor need to be a higher-level thief than the trainee, or have a higher percentage for the skill(s) being increased, or both?

How does the cost and duration of this training depend on the number of percentage points are being shifted?

[venger]

You can shift however many points you earn per level, per training cycle.

Self training is sufficient as that's how you advance anyway.

It's 2d6 days per training cycle.