Piping to xargs is a dirty way of doing that which can be done inside of find.
find . -type d -exec chmod 0755 {} \;
find . -type f -exec chmod 0644 {} \;
You can be even more controlling with other options, such as:
find . -type d -user harry -exec chown daisy {} \;
You can do some very cool things with find and you can do some very dangerous things too. Have a look at "man find", it's long but is worth a quick read. And, as always remember: