the basic math shakes out to be pretty much weighted against you.
The chances for success (without succeeding in the instruction task and ability modifiers already applied) are:
60% to succeed in grinding the herbs
45% to succeed in infusing the oil
40% to succeed in mixing and emulsifying.
So your chance to succeed in at a single salve at base level is
60%*45%*40% = 10.8%
with the successful instruction task it boosts each chance by 10% so it shakes out to
70%*55%*50% = 19.25%
It is definitely a tough challenge and the odds for a single attempt were against you