With the colour paper, it's basically impossible to expose by inspection. Plus I'm only using an 8x10 contact proofer so not split-back anyway (and my only splitback frames are medium format sized) so I do testprints, covering up part of the frame and moving it along like you'd normally do, in 2minute increments for my UV facial tanning unit. That one took about a 4 minutes exposure.
Thanks, very interesting. Sometimes you need to see other people's work, especially in the alt. processes, because it can lead to you exploring new avenues of expression.