Created a account to share my experiences.
I ruined my first sensor for my 450d. Thankfully there are some refurbished sensors going pretty cheap on eBay(US). I was successful on my second attempt. I learned from my first sensor that, at least for the 450d, the sensor is surprisingly durable. I tried scratching the dead sensor with a wooden pick and found you would need to apply A LOT of pressure. The easiest way to remove the glass protecting the sensor is using a hair dryer at the lowest settings. I'm sure others have done the same but I can confirm this works beautifully along with an x-acto tool. I was able to remove the glass in one piece. I found that using a bamboo cocktail pick works wonders as a scrape tool. This along with the Meguiars PlastiX used by conehead, can all be bought on Amazon. I initially scraped away a small amount of the bayer filter with tweezers VERY gently. An opening will be enough to start scraping away with a bamboo pick sharpened to a blunt but also sharp tip. I then polished with the plastix with a q-tip very gently. I've attached my flat and it is far from perfect, however I will count my blessings as I think it is good enough. It's nothings flats and dithering can't take care of. Of course with the timing in everything in this hobby, I have cloudy skies the next few nights so I cannot test this out on DSOs. But I will share my results when I do get a chance.