I like XCACLS.EXE from the NT or Windows 2000 Res kit.
To set the user permissions in a folder called F:\users
for /D %%I in (f:\users\*) do xcacls F:\USERS\%%I /T /E /G %%I:c
This assumes that the folder name equals the users name and that you
want to give them Modify permissions. If you do this from the command
prompt, use only one %. If it's in a batch file you need to use two %.