The terra cotta trays work great. Some people pick up a cheap pizza pan from wallyworld or some place similar.
Torch or weed burner is the preferred method of starting coals for a lot of people.
FYI, the way a fire basket is designed for a UDS, a door isn't really needed. You should be able to maintain temps for far longer than it would take to cook anything. Think 14-16 hours @260, depending on the type of charcoal used.
Some people have added a third rack close to the fire basket and use it for the diffuser. I don't see why you couldn't have 3 cooking racks, but most people go with 1 or 2. I've used my lower rack to place a diffuser on before.
Modded Brinkmann Gourmet. Basic UDS. Rescued 22.5" OTS. SJS Mini-WSM. Stubbs. B&B Oak Lump.
Cannondale 2009 F8 (for burning off all the great BBQ)