Me too.I use Matrix MP 200 DTM (direct to metal) Primer, MP 210 DTM Primer Sealer and MP 3 High build primer.
All 3 are urethane. They all sand well. I don't have abrasive buildup with regular "sandpaper" but I switched to a Mirka dustless vacuum system for my DA Sanders which uses a "net" style abrasive versus paper backed.
Never tried SPI, TCP or Tamco but I swear by Matrix MS 42 high solids clear.