Michele, thanks for starting this thread! It's got me to thinking about this question and how I work... and what's more effective/efficient.
When am being smart
I work more slowly and deliberately as a painting is approaching completion --once have gotten the essentials and likeness in place and am to the stage of 'tweaking'-- and things can come along fairly quickly. Slowly and deliberately means spending a fair amount of time studying what's already there, comparing to references, and making lists of what little things want adjustment, then going in, fixing those things and knocking them off the list. If I'm being not so smart
and don't spend the time studying and deciding what really needs doing, but go in directly with a brush and tool around just generally 'fixing' things I can spend literally days (don't laugh!) reworking things and accomplishing virtually nothing (pictures taken before and after can be hard to tell which is which) or, worse --can be progressing backwards where 'before' looks better than 'after'! (Uh-oh)
Very rarely, there might be something I've procrastinated on and left 'til then end that might come together very quickly if am smart enough to have at it, then leave it alone. (Leaving things alone when they should be done is the hard part for me!
)