Once I become familiar with an artist's work I can usually see the way he draws as you describe. Ones like Pierce Rice, Ken Battefield, Ed Moritz, Maurice Gutwirth, etc. that I've been seeing since I started getting into GA comics, those I can spot looking at the whole body of the page. For ones I am not as familiar with, or have never seen before, that is when I have to study ears and other little "tells." Once I can spot those, then it's like a key opening a lock, and I can start seeing other things.
And I agree, Who's Who is a guide, not a bible. I frequently come across attributions that are off by a year, or are not listed at all. Take Daredevil Battles Hitler for instance. The GCD listings are not even close to accurate, and Who's Who doesn't even list most of the folks I've spotted as having done Daredevil in 1941. My attributions for that story are:
Chapter 1 (DD & Silver Streak): George Mandel
Chapter 2 (DD & The Claw): Unknown*
Chapter 3 (DD & Lance Hale): Harry Sahle
Chapter 4 (DD & Dickie Dean): Frank Borth
Chapter 5 (DD & Cloud Curtis): Emil Gershwin
Chapter 6 (DD & Pirate Prince): Harry Anderson (signed)
*I can’t shake the feeling that chapter 2 looks familiar, but I can’t place it. Maybe it just looks that way because I’ve studied it for so long. The closest I’ve come is possibly Edd Ashe, but I’m not convinced enough yet. I need to look at more of his work.
-Eric