I use the previous two suggestions in tandem. If you play with the FFCP a bit, you will figure out that you roll through your fingers in a loop, skipping a fret (sometimes by going to the next string 5 or 6 frets lower) between each finger except the two prior to the one you started with. Scales overlap - you start the next octave on the same finger you end the first one on, so you switch at that point. I wish I could explain it better. Once I noticed the correlation, I could find a scale starting anywhere with any finger. Now I am working on knowing the double stops within the scale.
"First you master your instrument, then you master the music, then you forget about all that ... and just play"
Charlie "Bird" Parker