I was late for a meeting when I posted earlier. I'm back now and will spend a little more time on your answer.
The major scale pattern:
G|---2---|-------|---3---|---4---| 1st string
D|---6---|-------|---7---|---8---|
A|---3---|---4---|-------|---5---|
E|-------|---R---|-------|---2---|4th string
Is repeated all over the bass fretboard. Place the R on the 4th string 3rd fret and the G major scale is waiting for you, i.e. G, A, B, C, D, E, F#. Place the R on the 4th string 5th fret and the notes of the A major scale are waiting for you, i.e. A, B, C#, D, E, F#, G#. Why? What note is on the 4th string 3rd fret? It is a G. 4th string 5th fret is an A. So if you start the major scale pattern on the root note, G, the pattern will point to only G scale notes. Just play the pattern and you have all the notes in the G major scale waiting for you. That F# automatically was placed under your fingertips, as were the C#, F# and G# when you asked for the A major scale.
Now as the bass fretboard is tuned in 4ths you can start that same major scale pattern on the 3rd string and to some degree on the 2nd string as well. If you start on the 2nd string you do run out of strings before your pattern completes itself.
The Major Scale Root on the 3rd string.
G|---6---|-------|---7---|---8---| 1st string
D|---3---|---4---|-------|---5---|
A|-------|---R----|------|---2---|
E|-------|---5----|------|---6---|4th string
Point in all this if you know where the root is the root's 5th will always be up a string and over two frets. The root's 3rd will always be up a string and back one fret. I find that helpful.
Now if you are not going to use riffs of R-3-5-3 or R-2-3-5-6 then it's not a lot of help. I play generic riffs of R-3-5-3. So I like this approach.
If you are faced with a C chord then R-3-5 will always work. Why? Well the C chord is made up of the 1 or root note, the 3rd note and the 5th note of the C scale. Now the song is probably in 4/4 time so you need one more note to fill out the measure. How about R-3-5-3 to fill out the 4/4 measure.
C7 chord R-3-5-b7
Cm chord R-b3-5-b3 or R-b3-5-8
Cm7 chord R-b3-5-b7
Cmaj7 Chord R-3-5-7
Cdim chord R-b3-b5
Cdim7b5 chord R-b3-b5-bb7
So I see a Cm7 chord I know a :
Root nothing will work
A Root-5 will work
A Root-b3-5-b7 will work
In other words I see a Cm7 chord - I mental say OK it is a C minor chord that means R-b3-5 and it has a b7 so I can if I like fill the measure with R-b3-5-b7. Now that took a millisecond.
Sometime the song calls for just the root and sometime the song calls for R-b3-5-b7.
If I know where all those notes are - piece of cake all I now have to worry with is establishing a groove.
This may come in handy:
http://www.smithfowler.org/music/Chord_Formulas.htm
Hope that helped.