On The Job Training, Help needed formulating a house rule. Options

[bibliophile20]

Running Ghost Cartels at the moment and, when plotting out the calendar of events for my notes, I noticed that this is a *very* fast paced and intense campaign; the karma is going to be flowing fast and freely, but the problem with the pacing is that there isn't any time to train. Skill advancement takes so bloody long that I find it unlikely that any of my PCs will want to step down for a while for a weeks-long training regimen, either in or out of character. Plus, there are such things as on-the-job training and learning by doing.

Thus, asking for help with formulating a house rule for on the job training; I have just two requirements that I've been trying to keep in mind, personally:
1. It should supplement the regular training rules, not replace them--i.e. I want this to be a choice between taking time off to train as the more efficient option, versus the on-the-job training, which will be less efficient, but doesn't require downtime.
2. A minimum of bookkeeping.

One idea that I've had but am thus far dissatisfied with:
Each time that a character beats a threshold with a skill that they've been training with at least one net hit, they may immediately make an Intuition + (skill) test, with a threshold equal to the skill rating +1; if they succeed, that then counts as one hit on the training test.

Not happy with this, and looking for suggestions.