I Noticed these didn't load in sequence, not sure why.
If you have a specific question or need help along the way, Please feel free to contact me,
Seth can put you in direct contact if it helps.
Yes, You can twist with a flex shaft, but remember that yellow gold anneals hot to quench, white, hot to air cool.
They also have different compression characteristics , yellow will compress easier than white, even when annealed.
Go slowly with your rolling mill and adjust in VERY small increments.
If you are going to fuse these together, use white flux only, clean thoroughly with sparex. Flux the solder and use a low melt point, preferably yellow solder, It will have less tendency to crack when compressed, You'll probably be better off with a hammer for control, being able to bias the strike more to the white material.
Gotta practice, I can only share my experience, someone else will possibly have a completely unique take on this.
Try contacting Jo Hammer... She's the best..