If you hold him against your chest and support his butt, he should be ok. If this fails, take one hand and gently rub his neck under the base of his ears, among the little folds of looser skin. This has the same effect as a mother's scruff, and will sometimes calm them down. Try not to touch his feet or tummy, that alarms most rabbits.

Every bun is different. Mine likes it when I rub a finger from the bridge of his nose, up his forehead, and between his ears. Almost puts him to sleep. I've had one that really liked it when I would nuzzle my face into her side, probably because I was warm. Another likes her ears rubbed.

If he needs to be upside down, try wrapping him in a towel, sitting with your knees up, and resting him tilted back against your thighs like a painting easel.