Hope you you find this helpful
-- using large brush to block in large shapes.
i found it easier to draw multiple larger shapes similar in proportion to one another than it was to draw multiple tiny details similar to each other in proportion.
--changing grey scale color of big brush to help differentiate major planes.
-- concentrating just on large shape and plane to start, then big brush eyeballs/nose/brows, then smaller brush brows, then eyeballs, then nose and mouth. I found separating the general overall shape and plane workflow with large brush from the smaller brush workflows allowed me to focus on one stage at a time. I found this process to be very fun.
--using photoshop navigator
--using eyedropper tool to sample tone so can continue to edit previous layers with same color
-- putting in folder all layers dealing with current process