I have been a long time user of KNB, but it makes a mess on my boat, even when I hold it out away from everything. I am not sure how, but it always ends up in little dots on my topcap. I don't find it lasts as long as I would like it to either, and have started getting much better results with a large tub of Crawfish scented Smelly Jelly. It stays where I put it, and lasts a good long time.
BTW - on the subject of scent. I have got KNB, Smelly Jelly, etc... on my hands in the past, and the stuff really "stays" with you, if you know what I mean. So I started carrying a bottle of Hunters Specialties liquid soap in my boat. I figured that if it does such a good job of removing the "stank" off of me before going deer hunting, that it should work well for this as well - and it does. I highly recommend carrying a bottle in your boat - if for nothing else, to clean your hands before you start handling lures - no matter whether you are using lure scent or not, it will help get rid of "your" scent before you start threading plastics on a hook, etc...
All the best,
Glenn