Accents for 2 voices

1. ctrl-select all notes you want accented then doubl-click the desired accent
2. copy doesn't work I believe.
3. Style → Edit General Style → Numbers.

Not sure what you mean about entering accents on a single staff. You can selecting as many notes as you want, on as many staves as you want, and apply an accent to all at once by double clicking the accent icon in the palette. Is this what you mean?no way to copy accents that I know of, although ability to comtrol what gets included in copy and pastel pertains is a common request I too would like to see someday.

As for measure numbers, I don't know a way to make them display on multiple staves in the score (edit after seeing the above, which crossed with mine - now I do!), but do note they are automatically included in the extracted parts even when not displayed that way in the score.