Layerizing Method For Layerizing, Color Separation & Recoloring Textile Print Patterns

I want to ask about Layerizing Method For Layerizing, Color Separation & Recoloring Digital Rasterized Textile Print Patterns. 

(For controlling the colors for printing on fabrics.)

Like floral patterns etc.

As far as I know there are two methods used for this purpose

Method 1) Separating Va Colors

Taking samples from the colors from the different color sections on the rasterized image then create swatches and separate the parts which colored with these certain swatches via color channels.

Method 2) Auto Trace or Manual Trace the different sections on the rasterizxed image. 

Question 1) Which method do you recommend? Is there other method do you recommend for another specific setting? Why?

Question 2) How to recolorize after layerizing?
Creating a fill layer and set the layer merge settign as "color" etc.?