Watch the Somethin' in Da Water online guitar lesson by Shane Theriot from Rhythm Mojo
This piece alternates between Bb minor and G minor, which are not relative keys, so you will have to switch keys and positions. Notice the way I force notes over the chords that are technically not in the key center (d) over Bb minor, but still make it work. Get the voicings together first before you tackle anything else. This will save you a lot of trouble in the long run.