I add coarsely cracked coffee beans (and/or vanilla beans) to the keg in a fine mesh bag and pull it when the flavor gets where I want.
Yep. Have done exactly this a few times with coffee and have gotten exactly what I wanted after about 24 hrs. If I were to change anything it would be the roast/bean of the coffee.
My local roaster, who has worked with a number of breweries on their coffee beers, says that you'll get full extraction from the beans in 24 hours, so going longer is not necessary.
I add coarse cracked beans to the keg and pull them after a day or so. I get flavor and aroma this way. I've also added espresso to the keg, but I prefer the flavor from adding the beans directly. Just make sure that you enjoy the flavors you'll get from the beans before you add them.
I stopped using vodka tinctures years ago, as I did not like the impact of the vodka.