Proper way to apply talcum powder to a GP-5?

I recently picked up a GP-5 and I’m trying to preserve the rubber as well as possible for collection/display and occasional wear.

I’ve heard people recommend using talcum powder on older rubber masks to help prevent sticking/deterioration, but I’m not totally sure about the proper way to apply it.

Do you apply it lightly with a cloth/brush, or just dust the interior and shake out the excess?

Also, is it generally recommended to wash the powder off before wearing, or is a very light coating considered fine?

Thanks.