I learned a lot about deep litter from an excellent BYC thread where a poster gives us not only how they did it but what the results were after a year. The thread can be found here >
https://www.backyardchickens.com/t/643302/results-from-first-year-with-deep-litter-method
I've been doing it for several years and love it. I clean it out during the spring/summer and throw the litter in the compost for the garden, then begin again. The concept is that - done correctly - deep litter will break down much like your compost pile will. You continuously add pine shavings, leaves, shredded newspaper, any type of organic bedding material [except straw as it takes so long to break down and can get nasty] and the microbes and little critters attracted to such will cause it to break down. While you continuously add stuff, it's also being broken down into smaller bits. I bag shredded leaves every fall and add them continuously throughout the winter.
It's not the amount of litter that you add that helps warm things up, it's the composting action within the litter that generates heat. Just like your compost pile will be a bit warm when you shove your hand in it, good deep litter will do the same thing.
Done correctly, deep litter doesn't smell. You need to keep adding organic material to prevent smell. And, yes, sometimes it can get too dry and that will cause the composting action to slow down just like your outdoor compost pile. That rarely happens as usually the chicken poo will supply adequate moisture and the litter will even take moisture from the air but - if you've a large coop with few chickens and are having a dry spell - it can get so dry that you'll kick up dust just walking in the door. When it gets like that I'll give it a little sprinkling from a gardening can, just a tiny amount to pull the dust down and get the compost rolling again.
Deep litter works best on a coop with a dirt floor. Mine isn't dirt so I inoculate my coop with a few buckets of dirt from our woods every year. That dirt has all the leaf and debris eating critters and microbes in it and they get to work digesting the litter and poo.
It's a little work to get it rolling correctly but once you've invested that time and energy, deep litter is self-sufficient. Take a peek at that thread I mentioned above as I learned a lot. Good luck!