I like to let the air out after seating the beads
this way the tube can relax - hopefully letting wrinkles unfold
maybe even bounce it on floor to help
then put air back in to final pressure
also I always put the tube in the tire with a small amount of air in it
this way avoiding some wrinkles and helps stop the tire irons from pinching tube
somewhere a guy showed the right amount of air was such that the tube would
just kink over one of your fingers.
I also use baby powder - will have to check if it has any corn starch ?
'11 Dakar 990