Lamenting not knowing many jammers these days but, I found the most useful tip I ever got about learning manual skills was to do a little every day but not a whole bunch every week.

Dont know why it works but it does; my last bit of improving was flatpicking Celtin Reels, I never imagined I could do it, but hey - I got it done and IT is original and very nice to listen to as well as play. Now before you gallop off to try it or dismiss my achievement - note I can only play at slow tempo - 110 BPM two beats the click or 220 and I pick realy easy tunes like the Silver Spear. Always I do them with open fingerings and no capo - It is harder to get it down but well worth the effort.