I have done somethng like this many times. I will open a credit card, I always receive very high limits, such as 50k 75k. I then purchase several refundable F tickets on UA or AA (they give faster refunds), wait until the miles post on AA, Starwood, etc. Then refund the tickets and close the account leaving only a negative mileage balance with the credit card company.

I recently did it when I needed 70k additional airline points and 40 starwood points.

works like a charm!