I have never used rail lube. I have seen many crossbows that wouldn't cock no matter how hard you try. The trigger boxes are all gunked up with rail lube and once they are cleaned they cock perfectly.
I will say that if you must use rail lube...just get a can of Jig-a-Loo and spray it on a rag and wipe your barrel. It's a dry film lubricant and won't gunk up your trigger box.
Most rail lubes collect dirt and will scratch your barrel. I had a PSE copperhead in this summer that looked like somebody had taken 80 grit sandpaper to the barrel. The owner said he shot about 250 shots. I had a Copperhead that had over 1000 shots on it and no rail lube. The barrel looked new.