Found the best way to boost Medicine to 20 easily.

[kahlzun]

Attach Artificial or Bionic limb to pawn (~2000 skill @ Interested)
Operations: Remove Part (~2000 skill points)
This will leave the pawn bleeding, patch them up (~200 skill)
Operation: Reattach Part (~2000 skill points)
rinse, repeat.

Practical example:
Surgeon with a Level 18 Medicine (14904 skill pts) and "Interested" (1.0x speed)
Removes Bionic Leg (14904 -> 16900 skill pts)
Treat bleeding (16884 -> 17376 skill pts)
Attach Bionic Leg (17360 ->  337 skill pts @L19)

(Note the skill point drop between the set. You lose 4 skill points every few seconds at these skill levels)

Total cost: 3 "Herbal Medicine", game states value of $5/per, for approx 4000 skill points (about 1/50 of the skill points required to get all the way from skill 0 to skill 20)

I feel a little bad for doing this to my pawn, especially as he did just join my colony, but it works really well..

Don't know if this is well known out there, but i only just realised it was possible.

All it costs you is 3 medicine, and if you are harvesting Xerigium, you should have piles of it.

[b0rsuk]

You will still need a hefty supply of good medicine to do it reliably. Or a very good surgeon. If you have a skill 18 surgeon, those +2 points are marginal.

[mrofa]

There is a chance to get catastrophical surgery and the colonist you oparate might die. And there is also the most precious resource used, whitch is colonist time that he coulse spend doing something else, assuming they guy you oparate is a prisoner and not another colonist.
So in the grand scheeme i think you shouldnt feel bad, since its kinda balance itself out

[A1win]

If a colonist has 118% (1/0.85 to be precise) or higher surgery success chance, they can do surgeries with herbal medicine without a chance of failure, because 118% * 85% = 100.3%.

Hospital Bed also adds to surgery success chance, but it doesn't say by how much. I suppose it reads in some config file but I haven't looked.

[mokonasakura]

I have a reliable way that doesn't involve a chance to kill your colonists. Capture prisoners in one room and set them all to no interaction. Now they beat each other up forever allowing your to patch up simple bruises. Free medicine skill.

[kahlzun]

If a colonist has 118% (1/0.85 to be precise) or higher surgery success chance, they can do surgeries with herbal medicine without a chance of failure, because 118% * 85% = 100.3%.

Do we know how the success chance is calculated?

You will still need a hefty supply of good medicine to do it reliably. Or a very good surgeon. If you have a skill 18 surgeon, those +2 points are marginal.

I didn't get her 'out the box' as an 18 surgeon. I think she was 9, or 11 when i got her.
Even exclusively using herbal medicine (because i'm cheap) i only had one minor surgery mishap (while removing his leg, she sliced his kidney somehow).
And a level 20 person doesn't suffer skill level loss, which at the higher levels gets quite egregious, which was what i was aiming for.

[TLHeart]

Start at 100%.

Skill level 14 = 95%

Consciousness 89% (100% importance.)
Sight 100% (40% importance)
manipulation 96% (40% importance)

final value 85% success chance.

Al this information is available on the colonists stats page, accessed from the "I" on the colonists pane.

[kaptain_kavern]

I have a reliable way that doesn't involve a chance to kill your colonists. Capture prisoners in one room and set them all to no interaction. Now they beat each other up forever allowing your to patch up simple bruises. Free medicine skill.

This and melee weapons hunting :p