You can train trapping by setting and resetting a snare trap you bring with you. Note, however, that the spirits don't seem to like excessive setting of traps, and they don't seem to take removal into account. At least that's my explanation for why I got a fairly bad relation for no apparent reason.
Working 'till you drop gets boring when it results in constant interruption of work, though, and for a number of tasks (e.g. hide working) I want my character to have zero fatigue (at least until it's I've failed the first step, so there's no high quality to maintain).