To recursively give directories read & execute privileges:

find /path/to/base/dir -type d -exec chmod 755 {} +

To recursively give files read privileges:

find /path/to/base/dir -type f -exec chmod 644 {} +

Or, if there are many objects to process:

chmod 755 $(find /path/to/base/dir -type d)

chmod 644 $(find /path/to/base/dir -type f)

Or, to reduce chmod spawning:

find /path/to/base/dir -type d -print0 | xargs -0 chmod 755

find /path/to/base/dir -type f -print0 | xargs -0 chmod 644