The proper headers for skipping channels follow this format: (channel)(instance #)("skip") the Value under the headers need to be TRUE
For example: to skip eBay main you would put ebayskip because the main channels are not considered an instance for ebay/amazon with a value of TRUE.
Furthermore, on the backend we shorten amazon as amzn for the purpose of our headers so to skip amazon main it would be HEADER: amznskip value: TRUE
Last example would be for an instance, so for ebay instance 4 it would be HEADER: ebay4skip VALUE: TRUE
As always with anything in bulk we reccommend you try it on 5 or fewer items first.