Yep. The biggest mistake that I see trollers make; is trolling too fast. Slower is usually best. However, occassionally bumping up the speed--and then backing OFF fast on the throttle--has been proven to catch fish. Its the sudden change that triggers a bite sometimes.
Most also do not understand the concept of the "S Curve" trolling pattern. In other words, don't just troll in a straight line. Making turns, will drop the gear deepers on the inside of the turn. While the gear on the outside of the turn, will raise up. This trick will also trigger bites.
You also may have been either too deep--or not deep enough. So, varying your depth will help too (as will a variety of flashers/dodger, spinners, spoons, colors, etc).
Don't rely on just a single scent either, on your bait. Take several scents along, and find out what works (and it can be different from day to day).
Try different baits as well. Corn is a proven bait; but don't ignore others. Grubs sometimes work; as do others.
BTW, these principles apply when trolling for other species too. Not just kokes.
Good luck.
P.S. It is indeed a learning process.