I know you didn't want to do this, but for $40 my local powder coater will media blast a frame. Every nook and cranny is clean metal when through, and the surface is perfect for paint or powder to adhere to.
That's what the professionals do to prep a frame.
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If someone tells you that you have enough bicycles and you don't need any more, stop talking to them. You don't need that kind of negativity in your life.