Hi,
After working as a proofreader in a large video game company (publisher of Skyrim) for 3.5 years, I am taking a break for a while, and have a lot of time on my hands, meaning I'm available to work on your project starting right now, for a quick turnaround.
The way I would usually work would be by starting with a quick read through of your project, to get a sense of the tone and context and understand your field of work, which I usually find to be as important as correct grammar and spelling. Then I would perform the actual proofreading, making sure your text matches both the appropriate tone and context, and is of course in proper English.
If you have any questions, I'd be happy to answer them.
Have a good day,
Arthur