Fred Hammond is excellent!
A fun thing is to mix techniques such as slapping Gospel. It's not as easy as it sounds at first because of the mental association but it's a good exorcize. Or if you've never put alternative timings into things; try it. Playing with a pick can be a real challenge if you've come up with fingers and slap.
You need to find what challenges YOU. The thing that helps me - is to maintain discipline in NOT playing what's easy or familiar. We all like to sound good & new things take time. IMO - it's the things that demand discipline due to the challenge that makes my progress. If I play things which don't demand that I concentrate on a new technique of learning element; I get stale and play the same material.
A lot of different material helps me such as drum timing lessons.
Now there was something that I was looking for: it's a simple "Amazing Grace" in ONLY harmonics and it will teach some VERY fine touch if you just keep plugging away at it:
When you see 3.2 that means to play just pass the third fret and 3.8 would be just before the fourth fret.
You know the timing. So you get the harmonics down and then you shake the timing up to faster / slower, etc. but the whole thing is played in just harmonics & your touch will get very fine as does you appreciation for no longer looking at the fret-board. I learned this on a fret-less as a way to stop looking & letting my ear doing the driving.
G----------------------------------------------------------------------------
D-----5---3.8-5-3.8-------5------------5---3.8-5-3.8---------3.2-------------
A--5------------------3.2--------5--5-------------------3.2------------------
E----------------------------3.2---------------------------------------------
G----------------------------------------------------------------------------
D-3.8--3.2---3.8--3.2--3.8----5-----------5-5------------5--3.8--5--3.8-----5
A-------------------------------5--------------------5-5----------------3.2--
E-----------------------------------3.2----------3.2-------------------------
It can be a LOT of fun.
