Use:

magic:~$ more /var/local/scr/rw
#!/bin/sh

echo Remounting /usr read-write
if [ ! -z "`cat /proc/mounts  | grep '/usr '`" ]; then
        mount -o remount,rw /usr
fi
if [ ! -z "`cat /proc/mounts  | grep '/usr/local '`" ]; then
        mount -o remount,rw /usr/local
fi