mounting read-write, access denied?

[hscai]

Hey guys, I have a problem. Every time I try to mount as read-write, it gives me something along the lines of "operation not permitted" or something. (As a result, my original plan of removing stock Verizon programs were foiled.) I searched around the web, and found something along lines of this.

From the SDK's tools directory, run adb shell. In the
prompt run the following:
# su
# mount -o rw,remount -t yaffs2 /dev/block/mtdblock4 /system
# chmod 777 /system (Or any subdirectory you want to push to inside system)
# exit
adb push <local file> <device location>
and eventually you should restore the original directory permissions by:
# chmod 755 /system (Or any subdirectory you modified permissions to)

Will this solve the problem? If so, I don't understand much of it. What is "chmod 777 /system (or any subdir you want to push)"? What is "chmod 755 ..."? In the directions, what are you doing, and what are you supposed to do?

If this doesn't work, what's wrong, and what will fix it?

Conditions: Windows 7 64x, running as Admin, 2.2.3 build FRK76, rooted using MotoCache1's SBF method.


EDIT:

Figured it out. Simple, really: I forgot to apply su before mounting it.