When you flat (b) a note, you lower that note 1/2 step. When you lower a note, you are moving down/to the left on your keyboard. So, no matter how many flats (b) you have, lower the note 1/2 stpe for each flat (b). Examples:
Cb = C lowerd 1/2 step
Cbb = C lowerd two 1/2 steps
Cbb = C lowerd three 1/2 steps
etc.
When you sharp (#) a note, you raise that note 1/2 step. When you raise a note, you are moving up/to the right on your keyboard. So, no matter how many shaprs (#) you have, raise the note 1/2 stpe for each flat (#). Examples:
C# = C raised 1/2 step
C## = C raised two 1/2 steps
C### = C raised three 1/2 steps
etc.
The key here is when you are playing in a key that contains sharps in the key signature, then rename all notes as sharps. So, for the keys of C, G, D, A, E, B, F#, and C#, name your notes like this:
B#/C, C#, D, D#, E, E#/F, F#, G, G#, A, A#, B
Likewise, when you are playing in a key that contains flats in the key signature, then rename all notes as flats. So, for the keys of C, F, Bb, Eb, Ab, Db, Gb, and Cb name your notes like this:
C, Db, D, Eb, E/Fb, F, Gb, G, Ab, A, Bb, B/Cb