I was using Blend to trace a 2d newport shell sketch, and learned that little helper line segments, (or curves) was very useful in placing and slidebar modifying Blend curve fitting.

Also learned that after Blend has finished, the helper curves can be rotated, moved, or scaled, and the blend curves changes, and follows along.

Tried a Blend of cylinder edges, which also can be moved, scaled, or rotated.

In the attachements, the red is the original Blend. Other colors show modified Blends from rotation, and/or movement, and/or scaling.