They can mix.

Do you need a sticker with copper for peach leaf curl?

A single application should kill overwintering fungus without the need for residual (so long as not rained off right away).

The excerpt below suggest nooks and crannies are most important. Does anyone use a wetting agent (or are these in stickers anyway)?

I found the link useful, since the dangerous time is bud SWELL during COLD weather, which can be quite early in the new year.

Is fall a better time since drier and not freezing for a Cu+oil mix?

===== Excerpt:
The incidence of infection is greatest when rains wash the overwintered spores into the bud and cool temperatures lengthen the time that the emerging leaves are exposed to the pathogen, before they are fully expanded and can resist penetration by the fungus. When temperatures following bud swell are warm and early leaf development is rapid, infections rarely become established, even when spring rains occur.

Here is a link that might be useful: Peach Leaf Curl -West Virginia U.

I sprayed the first application. Then snow and rain. Looks like I'll have to do it again. thanks all, Mrs. G