The most tedious part of model building
Putty, sand, prime, repeat. This is tedious because sanding as a process is tedious. Add in the need to fill seams, fill gaps, fill surface imperfections, sanding on top of that, then primer to check if the fixed areas are truly fixed, the process can repeat itself. And depending on how anal retentive you are, one can spend weeks on the process. Below is a comparison between the initially primed hair and the same part after work was done to clean it up, fix the seam between one of the small hair pieces that came separate; and filling some of the holes caused by the pinning session. There is a small amount of clean up, but the part in the second picture is a leap ahead of the first in terms of surface prep and readiness for paint.