Sorry to break this to you, but currently the mce ir blasters ONLY work in mythTV in LIMITED fashion. What you need to do is grab yourself a USB Uirt which will perform all your blasting.
For the usb to work, there would need to be a template & driver created. With the usb_uirt, i have both of mine set up within 10 minutes.
1.get usb uirt
2. setup directv box templates in the webadmin
3. capture the box ir codes.
4. enjoy tv
1. same as above
2. creating the template. If you need to do this still, follow the directions you referenced in your original post. If its done already, then
3.you just need to capture the codes. You need the usb_uirt for this. Most reliable method i know of. Depending on where you got stuck, you may need to add your box, or it may be sitting there unable to communicate. Once you plug in the usb_uirt, make sure the controlled by box on your reciever is set to the usb_uirt.
4. Try it out. Make sure you reload the router after you change the controlled by box.