Yes, you are doing it wrong. You are trying to guess one note and then pick a scale that will fit everything. That will never work.
A solo, and especially a solo might contain several scales.
Listen to each individual note and try to find them. There are 138 individual choices on most guitars. So worst case scenario you have to play note on a 22 fret neck before you find the right one. Hopefully you can narrow that down rather quickly.
After you find the note, write it down. After you get them all then you can determine what the key/scales are that were used.
If you can't can't find a note tell us which part of solo and we will give you a hint as to which area of the neck to look in.
Use good speakers.