I use both the blue water eraseable and also the purple air eraseable for light to med. light fabrics. The air eraseable can be erased with a spritz of water if it's taking too long to vanish. Do Not iron over either of them.
For medium darks and darks I usually use a sliver of soap Like ivory. It stays on well for the actual quilting but wears off easily enough that I've never had to do anything to remove it when I'm done. I have one of those vanishing white pens, but I don't like using it because it takes a while for the marks to show and sometimes they don't show up which means re- marking an area.
I also tend to mark as I go since I mainly mark when I'm doing ruler work. If I'm doing regular Fmq I don't do much marking at all.
rob