My understanding is...
he is trying to MARK you just like he will mark his cage with his scent, he is marking you with his scent, so he knows you are part of his property/ territory.
when our gliders did this he/she would pinch my skin with teeth and it hurts some. they can do this for awhile so I would gentle move them away.
My wife's glider will groom her neck. arm. face for quite a while sometimes.