What's wrong with your buns? I just did a set of 65 seats, OE buns were perfect. Doing a 68 set now, OE buns perfect. 20 years ago I did a set of seats, 35 years old at the time, springs and frames rusty and broken, buns perfect. In fact, they still are.
If the buns are trashed, somehow, use the TMI product. Take your time, sometimes the foam around the list slot is too sharp and must be rounded off for smooth appearance. I use a high-speed air sander, sculpts the foam to whatever shape you need.