I’ll start with a disclaimer that I’m not a great piano player or an expert on piano technique but I do have a comment specific to this particular left hand line.
It’s basically an 8th note alternating low and high octave walking up and down 1,3,5,6,8ve,6,5,3 in Eb. Check out this video at 3:45:
It has a similar pattern in C except for the b7 in place of the 8ve. What I notice is the low note is not sustained but instead the hand rocks back and forth and the pinky moves in a crab-like fashion to the next note while the high note is being played. I think this opening and closing of the spread of the fingers and the rocking is the key to being able to play this line comfortably because your hand is not locked into the same position for an extended period of time. Boogie Woogie needs a lot of endurance so make sure you’re relaxed and not trying to play too hard.