Thanks, MM.
As for modes, I generally play what I have come to refer to as my "Blues-Penta-Dorian" scale which as the name suggests is a combination of the Blues, minor Pentatonic and Dorian scales.
Although in this particular track, some of the Dorian flats don't fit (possibly Aeolian?), so I just eliminate them and go from there.
It's all just top-of-my-head stuff anyway and I know that my "BPD" scale will cover just about anything, so I just play what seems to fit.
I know I should learn more about modes and specific notes, but sometimes I think it will take some of the fun out of improvising. I'm sure that will change as time goes by, but for now the "exploring" is fun.