You can have a mentor in a particular field...there's just no distinct registration for different areas.
Graduation from disciple ship equals:
coloring - 1900 skill
handgun - 1900 skill
longblade - 1900 skill
prospecting - 600 skill
rifle - 2000 skill
surveying - 600 skill
It's pretty early on that you get exempt from disciple qualification...when there's a word about something you do in your skill discriptions that doesn't sound plain negative. (I forget..maybe 10-15% of graduation requirement? this was in a beginners document somehwere...)
Anyways, it only takes afew days serious play to sink the opportunity for discipleship...but it takes a month or two moderate playing for a disciple to graduate.
Once you help them get the basics, help them survive, help them choose a profession to invest in...then the progress towards graduation begins.
It's really a tough road considering the turnover rate, but I'm getting pretty far off topic...as I tend to do. Adios.