There are many incubators available. A seven egg incubator can sometime be bought for less than twenty dollars. However, if you can afford to get a good brand. Those twenty dollar jobs work, but they do not last long.
What kind of quail eggs do you have? Those that have dark, speckled shells can be difficult to get a good image when candling.
I agree with Robin on the duck eggs. I'd recommend that you try Bobwhite quail or bantam eggs-eggs that are white. These eggs are easier to candle and learn with. An egg that is developing will develop distinct veins that are easy to see. This veining can be seen as early as the fifth day of incubation. Should a developing egg die, this veining breaks down quickly and the veins can no longer be seen. So, visible veins means the egg is alive and growing. No visible veins means the egg is infertile or has died and should be discarded. Once an embryo in an egg dies gasses form inside the egg shell. In time it can explode-and what a mess and stink.
Good luck with your eggs.