Hi Paul,
Yes, it is usually better to mix your mica with the FO / EO or even oil
before putting into the M&P. I don't always follow the instructions myself
and usually regret it.

If you add directly to the soap sometimes it doesn't mix as well then you
will get the clumps of color. When you use the soap you could come out with
mica on you. And the color doesn't blend.

From what I have read micas are usually NOT recommended for M&P because of
the clumping problem. So by mixing with the scent or an oil you avoid the
headaches.

Hope that helps you out a little.

Thank you,
Ginger Muenster
www.cosmicpotions.com