Many plants move into dormancy because of changes in light levels and temperature. It wouldn't matter how much you fed them - they're going to bed, thank you, see you in spring.

Autumn is a good time for putting on rougher compost. Think about fallen leaves, for example. They need all the winter (and a bit longer) to become leaf mould. Meantime, the worm population is up and operating in the top four to six inches over the cooler part of the year. Unless the ground was frozen solid, I suspect this would be true of northern areas, too.

Personally, I wouldn't fork it into the soil until spring, or during mild conditions over the late winter. Mostly I'd want that darker layer there to catch and hold the warmth to reduce frost damage, or blot up excessive rainfall.

In spring, I'd wait until the soil had warmed through before I put it on. I'd stir it through the soil, provided it was fairly ancient compost, because there would be enough warmth to come to continue the process of breaking down the compost into smaller elements for plant use. Or else I'd use it as a 'dressing' and mulch, particularly around the plants I know need lots of food and water.

thanks so much for sharing your thoughts with me!
~bobby