Cheers for the comments guys, much appreciated!
Been airbrushing some other kits last couple of days, so back into the Kranich tonight.
Jim, I was a professional solderer for 10 years, soldering micro components under the microscope. Especially during my years on the repair line, averaging 250 phones/ 8-hour shift, I would occasionally get a painful tunnel vision all of a sudden. Sometimes I couldn't see again properly for about 20 minutes.
What we had to do now and again was stop for a minute, and 'exercise our eyes' - blink a few times, and look up, down, left and right, concentrating on the corners of the room to get the focus back.
When soldering, I still use a microscope whenever possible, but for modelmaking the 'Mk.I eyeball', just checking work with the magnifying glass now and again (constant use gives me headaches)