They've tried the first couple tricks to no avail, but thanks for the link; I'll check it out for future reference.

I've always suggested/offered to swing my arm around a few times (centifugal force) cuz that always gets the veins bulging, but they're always quick to decline - quite animatedly.
I'd love to catch a naive student/trainee take me up on it one day... WHOOSH!
[Sound bite of Bugs Bunny from Bugs' Bonnets... "MY SPLURTING BLOOD‽ "]

Thanks,

Doc