Starting this to share my experience refunding.
First things first amazon is the easiest I have ever done. I double dipped an item worth about $300 first and then did a FTID on an item worth $1200. The $1200 item was obviously more complicated and took about a month. The second easiest place I have done is Nike, I double dipped a pair of shoes worth around $200. I've also done nike refunds for my friends multiple times. Urban Outfitters was also very easy, I did a partial refund and got about $400 worth of clothes for free. Pristine Auction is a place I don't see talked about on here. I got some basketball cards and the reps were tough, they only gave me store credit. I wouldn't recommended doing them just because everything on there is so overpriced and it is hard to turn a good profit for the time it takes. Flight Club is one I recommend because although it takes longer shoes sell for the same price deadstock everywhere. There is a $500 limit and they "investigated" when I did a empty package. The investigation took about a week and they gave me store credit. I have had two failed refunds they were because I tried too high value of items, they were both 1k+ items and they were from walmart and target. Fuck target the reps are useless. I just went to walmart and returned the items so I didn't lose any money but target I'm down about $300. I'm confident I could complete a smaller one ($200-$500) from walmart. I have a pending EB from bestbuy. If any of you want to share tips and experiences with stores PM me.