I use almost entirely maltodextrin and chocolate flavored whey protein as liquid food on doubles, 750 calories/bottle ~15% protein. I carry extra powder in Ziplocs. On rides longer than doubles, I'll add some fat and solid food. One doesn't really need the protein on a double, but it tastes good and makes one feel better. I definitely eat zero fat or foods containing fat on a double or on rides of a similar duration in the mountains. I plan for 250 calories/hour and weigh ~150, though I sometimes have some food powder left over.

I use a 2 liter Camelbak and stop ~every 50 miles to water and refresh my food bottle. I use Hammer Endurolytes to keep my electrolytes in balance, taking enough of them so that I'm just thirsty enough to need to pee about every 50 miles. I also use clip-on aero bars. I grease and carry a little bottle of butt grease for reapplication as necessary. I carry a spare pair of gloves.

150 miles/week works. More's better if possible and doesn't tire one too much. I do more climbing/mile on my training rides than on the event and ride them much harder. I don't normally do a training ride of over 5 hours, 4 is more usual.