Setting modes on directories vs. data files is sometimes a pain in unix, especially if you're doing something like "enable group write access" on a directory tree and its files, and the files are all data

Not particularly if you RTFM, provided you don't want to set completely different modes for files vs directories.

chmod -R a=rX,ug+w foo/
[download]

Note the uppercase X mode which means "execute bit but only if it's a directory".