Dew can be a real problem.
EPs, don't let them cool down as they will fog up as soon as you put your eye to them. Doesn't mean you warm them, rather keep them from cooling by keeping them in a foam lined case. Should they start to fog up, look at investing a few bob in a 12V portable hairdrier. Only bit of high-tech gadgetry I have plus a 12V car jumpstart pack.
What you did with the finder & telrad,
, good thinking. When they start to succumb to dew, see above.
The same for the secondary. A short blast of the drier is all you can do. Just blow of & a smidgen of warming.
If your primary dews up in a solid tube outfit, pack up & hassel the better half. Just allow the dew to dry of the mirror before closing the tude.
Do keep the dust cover off to allow the scope to cool, just have it tilted a little closer to horizontal so air just doesn't pool in the bottom and not exchange. A little fan speeds up the process.