More Precise Rotations

I was animating my Aclysm and Astrophe side-project and having trouble with a head rotation. I had created the character from a 3/4 angle and hadn't done a full rotation because I didn't anticipate doing too much animation; in my head they were just talking and not moving. When I got into the project, this worked for the depressed, lethargic, Astrophe character, but Aclysm is more wiry and energetic and having him not evoke that with body and head movements wasn't going to work for him. I tried doing it on the fly in Toon Boom, but it wasn't looking right; specifically, the head looked like it was being squeezed instead of rotating. It became clear to me that it would be worthwhile to do a full head rotation with a front, side, back, and 3/4 front and back.

Since I already had a 3/4 view, I started with the side and front, but when I finished them, the volumes from the front didn't seem consistent with the 3/4. The center line looked off. I was estimating and eyeballing where parts needed to be and I wasn't happy with that estimation. I thought if I did a top view it might help me to better visualize how the parts of the face related to the front and side. When I finished though, I realized I could precisely determine where parts would be in a 3/4 turn by simply rotating my top view 3/4 then cross referencing that with the side and front views. It was especially helpful in determining how much something would shrink as it got farther away from a viewer.

I applied this trick. Then I realized that I could cross reference a rotated side view with a front view to make a more precise top view. I went back and did that (luckily, it didn't change the 3/4 I had already done). I further applied this trick to an upward 3/4 as well. A common trick for creating back and back 3/4 views is to silhouette the front and 3/4 views respectively and I've done that below.

My rough designs, drawing through the character:

My final, inked results with angles explained:

This character is supposed to be a scraggly, wiry character and I wanted to reflect that somewhat in the design elements. You may notice things don't line up exactly at every single point. That's because either it was a design choice in that I wanted to avoid a tangent or liked the asymmetry of matching elements; I have imperfect strokes and the width varied (again, I like this for the character); or because I was subconsciously making excuses for not fixing minor things.Given that points match up better than I could do without using this method, I'm okay with minor imperfections and I'm confident that they'll never be an issue in a 2D animation or 3D model.

By starting with a front view, then lining a side view up with it, I can extrapolate most of the other angles I need by lining them up with other, sometimes rotated, angles.