Theres really not much you can do. I have heard of people putting JB Weld and other puttys/epoxies then painting to fix the cracks, however I wouldn't recomend it and it doesn't prevent more cracking.. Just stay low while on the job.
Is it the paint or the helmet itself? My 06 N5A that I just retired has some cracks in the paint from a flashover but the leather has not cracked at all.
the repair technicians form cairns told me to use JB weld to fix minor dings and to fix the seam if it was cracking. they said the only three reasons to take the leather O.O.S is
1.) the metal reinforcement wire is broken or largely exposed.
2.) there is a hole in the leather shell.
3.) if the rib stitching is broken and coming apart