You can apply or topdress with compost any time you like. I typically apply compost as a mulch as soon as I've finished cleaning up from winter so I am preparing to layer it on now.

How "unfinished" is the bottom of the bin (not that finishing is necessary :-))?

Thanks. That is good to know. The bottom pile is from November. Has c grass clippings and fall leaves, rotated only during last 1 month.

I am concerned mainly about top dressings getting washed off in the rain as I had read somewhere.

Unless it is applied on a pretty strong slope, compost does not wash off in rain.

Got it. Strong slope is not what is there only a gentle slope. Thanks.

But it has to be after winter as you mentioned. When the temp is consitently above freezing.