Ask them to hold there cock against everyday objects, like a TV remote control and really take the mickey saying things like "wow" you only just reach the red button, what a shame as my bf goes right up to the sky button" as them if they have a ruler to measure it. Humiliation on cam is quite difficult (don't do camming anymore) as they often want you to do all the talking & get little back to bounce off them.
If a pre-arranged cam ask them to have felt tip pens etc to draw faces on their penis, fake hair etc and make them dance on cam.
I found with any humiliation bookings that they do enjoy being laughed at a lot, so just repeat what a tiny pindick they have, what a useless lover they would be. That there only use would to be a sissy maid in pink frillies and maybe made to fluff big cocks for you (God sorry if this is too graphic ladies) anyway it used to get them going. Cuckolding, sissification etc seems to work. Hope that helps a little. XXX