I love to use fish oil, and I use varieties of it also. Coons are naturally curious, but satisfy their curiosity once or twice without catching them, and you better make a completely differently looking set or completely change the recipe.
I run a lot of dryland dirthole sets targeting just coon. Fish oil is the perfect dirthole bait, I've found. It has a ton of food appeal, but a reaching/grabbing coon will work a dirthole hard trying to get a handfull of food where the scent is coming from, but never has any bait to steal. I squirt mine oils right down into the bottom of dirthole sets, where I want their attention. A double dirthole set with a single dirt pattern in front of both holes is a killer dryland coon set...they will work both holes like this, with a lot of feet shifting to get better position to get into the holes. I get few misses with double dirtholes like that.
Yes, I've run trails of the stuff up to sets also. I think coons are a little near-sighted, but seem to have a decent whiffer on the end of their face, provided you are on site in a good location. They are not coyotes or foxes by any means, but stay close to hot trails and you can certainly pull them off with a trail to investigate a set. I've always felt that only two things were critical for getting a coon to come over to a set: (1) is visual attractors, such as a big dirt pattern, torn up look to a set, big pocket or dirthole, etc. and the other is (2) scent. Not positive which works first, I think the visual and then the scent keeps them their just long enough to work the set to get caught. I think in use of oils for trailing them up to a set, it may reverse and put the scent ahead, but either way it plays on what I've always felt were the two top reasons for a coon to come over to check out a set anyway.
If it works for you, Tim, keep it up. The cost of a buck or so of oil will trail a few coon to your set, and pelt prices should more than offset it. Not to mention its way more fun to check sets that have a coon in them than empty sets. Way to go!
jim-NE