This is entirely do-able by yourself with some practice playing two controllers at the same time. If you don't have someone else to play coop with or are just looking for an interesting challenge and don't want to get bored playing through the songs on lower difficulties, I highly recommend trying this.
For context, going into this I was already really proficient on expert difficulty (30+ fcs). I was able to 5* all the songs on easy within 2-3 days as well as medium within another 2-3 days. In both cases, I was playing ~5 hrs per day.
The challenge here is finding a controller setup that works for you and learning to read both charts at the same time. I found this very similar to playing piano once I started to get the hang of it
Now for controllers:
Normal controllers kind of suck bc you have to use the shoulder buttons and it's kind of awkward to get the muscle memory down. I did a few songs with the shoulders and quickly decided it was not worth the hassle of learning.
Instead, I used a Horipad controller with re-mappable buttons which I happened to have lying around. This allowed me to remap the shoulder buttons on to the face buttons in a linear row. I can add more details on the exact remapping and controller position if anyone is curious.
Guitar controllers are super ideal apart from the strumming. Strumming requires two hands so that is out of the question. I combined a guitar controller with a CronusMax so that the xbox would treat it like a normal controller (aka no strumming required). Then I remapped the buttons to I could play the neck buttons keyboard style.
Finally, starpower is also tricky. I tried taping the back buttons down to see if it would always activate immediately, but the game seemed to only recognize it as one press and the buttons would have to be released and pressed again to activate another time. For my setup, I wrote a CronusMax script to constantly press & release the back button on the guitar controller. Then, I was able to activate with just back on the other controller. I dedicated my pinky to activating starpower, which was ok but it did mess me up a lot trying to time the back presses in line with the other notes.
As for difficult songs, here were the ones I thought were the hardest on both easy and medium:
- Raining Blood - probably the hardest song across easy & medium, lots of faster
strumming and rhythms, no easy sections to
accumulate points on, solo is really weird to play both parts on
- Pride and Joy - that shuffle rhythm with little riffs in both the lead and rhythm
make it hard to find easy sections to get points, lots of improv-y
- Helicopter - has some of the faster strumming sections across both easy &
- Black Magic Woman - lots of syncopation in the rhythm and most of the lead is
improv-y in nature
I'll probably see how hard goes but I doubt it would be possible given the heavier chord/strumming use and more notes in the solo.
If anyone wants any more info on this strategy, let me know. Although I imagine not many ppl are still trying to knock these out in 2019.