"Again, the 3 draw is it" states Kim Wilson

"Again, the 3 draw is it" states Kim Wilson in his interview. Control, and use of the 3 draw is one of the most common indicators of a highly-skilled harmonica player. Think of the use of the 3 draw in the list below...

The "3 Draw Rule" in 2nd Position
I7 = 3 (or slightly bend, at the quartertone, for bluesy effect... or 3' if you're in minor)
IV7 = 3'
V7 = 3"

2nd Position
I7: 3 = 3rd of the Chord (light) / 3' = Flat-3rd of the Chord (bluesy) / 3" = 2nd, neither indicates major or minor, which means it's a universal note... when held, it takes on the function of the 9th (jazzy) / 3''' = Not used / Note: I7 phrasing "can" trump other chord changes (reference "Improvising Study 1 - Chorus Forms")

IV7: 3 = Major 7th of the Chord, only used in passing from a 3' (bluesy flat-7th) to the root (4+) / 3' = Flat-7th of the Chord (bluesy) / 3" = Major 6th, a common note used in grooves with a light feel / 3''' = Not used / You can use 1st Position I7 licks here

V7: 3 = Major 6th, a common note used in grooves with a light feel / 3' = Not used / 3" = 5th, used all the time / 3''' = Used in a 3rd Position lick on the V Chord

3rd Position
I7: 3 = Major 6th, a common note used in grooves with a light feel / 3' = Not used / 3" = 5th, used often (though most common in swing, as part of the arpeggio) / 3''' = Flat-5th, used all the time for a really bluesy effect / This chord is the same as the V7 Chord in 2nd Position / Note: I7 phrasing "can" trump other chord changes (reference "Improvising Study 1 - Chorus Forms")

IV7: 3 = 3rd of the Chord (light) / 3' = Flat-3rd of the Chord (bluesy) / 3" = 2nd, neither indicates major or minor, which means it's a universal note... when held, it takes on the function of the 9th (jazzy) / 3''' = Not used, though if you're using repetitive phrasing (chorus forms) and not acknowledging the IV7 Chord, then go for it / This chord is the same as the I7 Chord in 2nd Position

V7: 3 = 2nd, neither indicates major or minor, which means it's a universal note... when held, it takes on the function of the 9th (jazzy) / 3' = Not used / 3" = Root, used all the time / 3''' = Not used

1st Position
I7: 3 = Major 7th of the Chord, only used in passing from a 3' (bluesy flat-7th) to the root (4+) / 3' = Flat-7th of the Chord (bluesy) / 3" = Major 6th, a common note used in grooves with a light feel / 3''' = Not used / This chord is the same as the IV7 Chord in 2nd Position / I7 phrasing "can" trump other chord changes (reference "Improvising Study 1 - Chorus Forms")

IV7: 3 = Not used / 3' = Not used / 3" = 3rd of the Chord (light) / 3''' = Not used

V7: 3 = 3rd of the Chord (light) / 3' = Flat-3rd of the Chord (bluesy), not common / 3" = 2nd, neither indicates major or minor, which means it's a universal note... when held, it takes on the function of the 9th (jazzy) / 3''' = Not used / This chord is the same as the I7 Chord in 2nd Position