I find brown eggs really hard to candle.
Could be I'm imagining them, but I think I see veins in that egg.
I usually only candle 2-3 times. Usually around day 7, then perhaps around day 14-15, then again at 18 or so. I just usually pull anything that is totally obvious that looks gross or non viable or clear eggs(no development). The rest I leave and let them go to day 23 or so. This is when I use the incubator.
For broody hatching, I usually do the same. Sometimes maybe 4 times if there's quite a few clears or questionable ones.
I'm for sure not very good at candling. Especially Quail eggs I can't see a thing so don't even try! I set those and just wait for 17-19 days to see how many hatch

It's a SURPRISE every time, teeeny babies.
This blog/website is usually what I read/look at every time I hatch. She's got some examples and photos of the different days/stages and I *think* video too if you dig around. You have to scroll a bit, but the info seems to be pretty solid and I've found it helpful.
https://www.raising-happy-chickens.com/incubating-chicken-eggs.html