My 9-5pm day job consists of managing, uploading, creating and transferring listings for over 1,000 SKUs from Amazon, Ebay, Gunbroker, and my company's own website which is tacticalintent.com.
I have a solid grasp on creating flat file feeds and submitting them, as well as dealing with a range of other Amazon Seller Central issues.
I just started freelancer, but if you would like to see examples of my work in this field you could check out the website that I mentioned previously.
Let me know if you would like to know anything else!
Regards,
Micah Johns