Pete
An enzyme product will contain lipalases which break down fats, so you could prespray , work in and leave for 20 minutes before extracting.
However I think we sometimes make things too complicated, get temp up to 70c, intank or inline detergent and just clean it.
Make sure you run some water into a bucket or into the tank so that the temperature is near to 70c, should clean fine.
Cheers
Doug