Rob, there's another angle. Apparently the brain's neurons are attached to the auditory areas. When you practice, you change the brain. Testing reveals that these neurons are stimulated when practiced and then, here's the interesting part, they are also stimulated
by thinking and hearing in your mind without playing. In short, practicing "in your head" away from the instrument helps.

Another factor, you can literally practice in your sleep. Before retiring, go over the pattern you want to learn, think about it and in the early waking hours of sleep, it will congeal. You wake up the next morning knowing it better without having to have spent hours playing it.

If you are interested in a solo fingerpicking approach to the guitar, learn some classical pieces and there are good transcriptions of Chet Atkin's arrangements. (I think they have tab).

The best thing is to start at a playable level. You might want to check out Happy Traum's
basic arrangements of folk tunes (Homespuntapes.com). If you can learn to read music
on the guitar (if you don't already) you will save hours of time learning tunes.

The problem is that some people are endowed with a finger dexterity gene which means they can accomplish more technically than others. Emanuel is certainly an example.
Knowing where you are, in this, helps you decide what material is best to work on.
For example, I wouldn't advise attempting Lenny Breau's "The Claw" at this point.
In short, "grade" your material to your accomplishable level. Don't "bite off more than you can chew", so to speak.

The frustration level occurs when you attempt something beyond your playing level.
The approach best taken is learning a variety of tunes at your level and gradually moving forward. This has nothing to do with musicianship but it's about physical proficiency.