Are you asking about making a laminate?

If so, we just use a blending block.
I don't think I would cut something off the spline, but that's just me. If you are cutting it off the insert I would be comfortable with that as it's steel.
If you are asking about making the tube one color (or part of the tube), and / or the skirt another, I think most are dipping the second color (or in the case of the skirt, using the skirt mold).
This one was not dipped, but has the same effect / look as dipping.

This one was dipped in clear (for the eye), but could have been in any color to change the look:

Jason