One tip for indoor clay tracks:
I usually use Soft Ultra Flexx Turbo Trax but I spray them with brake/motor cleaner and brush in with a toothbrush a few minutes before the race. It makes the Ultra Flexx Compound very soft and sticky which is perfect for cold weather or indoor tracks where there is no sun on the dirt and it is a slick/slimy groove.

This makes the tire wear faster but is perfect for qualifying because the tire gets more traction the longer you run it.