Watch the V - II - I - IV Mixolydian online guitar lesson by Robbie Calvo from Modal Expose
I didn't take a scale approach to this solo at all, in fact I was thinking E9 arpeggios the whole time. Because my tonal center is so strong in this progression I decided not to give the other chords any power what so ever. My focus was to outline the E9 chord and have some fun creating some nice flowing lines.
I used four different patterns of the E9 arpeggio and of course took a liberty or two with chromatic passing tones! Does the use of chromatics,etc negate the modality of this progression? Absolutely not. The progression is resolving to the V chord, E9 and therefore it is modal by nature.
Modal purists may argue that using chromatics is forbidden and you will be punished:-). I say music is music and if it sounds good it is good. Modality isn't an exercise in Purism it's about making music! Next!