Well, I’m reminded of a comment that Chocolot has said several times, and I paraphrase: once you think you know what you’re doing, Chocolate will do something just to let you know who’s boss.
you should plan on tempering the colored cocoa butter (CCB) prior to using, anytime, any day, you plan on using. Always start with the basics.
is there a way to be “sure that when you paint a mold....”? That is the million dollar question for sure. I don’t believe there exists a way that will guarantee you success every time with CCB, but, there are methodologies that will help you.
These are things, steps I do, and my success rate is fairly high
temper your cocoa butter
use clean, polished molds
apply decoration
allow CCB to crystallize in mold prior to shelling
shell, fill and cap per usual
unmold
but step 3 is critical, as there are many ways to apply CCB, i.e. paintbrush, cotton swab, finger, airbrush, toothbrush, etc,