If that’s your main aim, you might baulk at the Jamie Andreas approach?
If you follow Jamie’s ideas the first thing you’ll do is slow down massively (in return for later gain). Jamie is very keen on the idea of making a very firm foundation to technique & that starts with looking very carefully how you approach the guitar. How you sit, how you hold the guitar, where your right hand is, where its fingers are, you left hand is, how its fingers approach the strings, how each hand & finger moves, etc. This is involves lots of careful observation and consideration. It’s not a ‘fast fix’ process.
Rather like using the IFR SingThe Numbers materials & sticking with just 1.2.3 till you have it really solid before even thinking about adding the 4?
I’ve had Jamie’s book almost a week now. In that time I’ve played far less notes on my guitar than I’d normally do. In some of the exercises you don’t play anything at all! However, I can see the sense.
I imagine her answer to your strength & stamina issue would be slow, careful work on hand position. Getting it just right at a very slow pace. Getting your fingers to move precisely & economically (i.e. minimum effort), across the neck (at first you are working with the left hand at around the 9th fret to get a good hand position, then over time you work towards the 1st fret aiming to maintain that good precise control). Initially working ‘no tempo’, i.e. slow enough to get it spot on without out thought of a regular ‘pulse’ to the movement (that’s where I am now), then with a slow metronome, then gradually speeding up from there, maintaiing that economy. That’s likely to be a slow, but sure, process. Months not days?
Another analogy might be like when I started doing yoga stretches again a few years ago? It took me 3-4 months before my toes first touched the ground in the Plough. It was worth the wait.