Hi there.
I am by no means an expert, but I find that if you are well prepared before hand it really doesn't take long to candle the eggs. I did it two nights ago in our coop at dusk while my hubby nursed my broody hen, and I got 9 candled in under 3 minutes!
Lay out a big fluffy towel on your bench, doubled over, to protect the eggs (just in case you drop one). Don't laugh - it happens!
Have your torch, with fresh batteries, on stand-by.
Place a basket with a towel in it to the side, so you can pop any rejects safely in there.
Make sure you have a pencil handy so you can mark any questionable eggs to be re-checked at a later date.
Only then should you remove your tray from the incubator. Start to work your way along each row, candling each egg carefully. It really should only take a few second per egg - once I spot veins and a black blob I'm happy.
Good luck!
Krista