Well, I haven't actually modified any servos for continuous rotation myself since I found Parallax have servos already made for that and they're not high priced. But I've worked alot with regular servos and read a bit of the tutorial now real quickly, so I think I can help you somewhat anyhow. First of all, the hex file is for the controller sending a 1.5ms pulse to the servo to keep it centered. The file is intended for the Atmega8 MCU so if you are using any other microcontroller you may need to create and compile your own file proper to your controller. (Especially if you're not using AVR) Most servos use 40 Hz which means you should supply the servo with a new signal every 1/40 = 0,025 = 25ms. Don't worry though, the servos aren't that picky, you can get away with lower speeds and sometimes even a bit higher. (keep it lower rather than higher though)
This setup should work:
1.5ms 25ms
__----------___________________-----------_________________------------_________
So, make sure you have a centering .hex file for your servo before you go to the steps in the tutorial. Tip: If you are using AVR there's a function in util/delays.h called _delay_ms();
#include<util/delay.h>
....
....
_delay_ms(#amount of ms you want);
...
...
Hope this helps.
/Nicky