I use dots to learn tunes sometimes. What I do is play a few times just from the dots, then I see how far I can get without looking at them. I use them as reminders for a while - only looking when I absolutely have to. It's possible you just need to play the tunes a lot more. After all, if you've memorised Bach and Mozart, you ought to be able to be able to learn fiddle tunes. I usually learn a fiddle tune about the same time as I get sick of playing it.