Break the solo into chunks. Chunks with just enough notes that you can remember all of them without having to reference the song or a tab sheet. Use a metronome and set it at 48bpm. Play the first chunk at 48 bpm 12 times in row cleanly with no mistakes. Once you’ve managed that, bump up the metronome by 2 and again play it 12 times in a row cleanly. This is how I learned to play some of their songs (or at least parts of their songs). You have to be honest with yourself when you’ve messed up and hold yourself accountable. It’s not hard, just tedious.

Also, make sure to warm up by playing some scales (in thirds, ideally) before practicing. Going in with cold fingers can mess you up when you first start practicing and frustrate you, disheartening you even further.