How do you get the slime out after water is drained out of the pool?

Rinse it out.

You can rinse it with a power washer. You can rent one from Home Depot for 1/2 day. If it is really bad (power washing doesn't remove it all) you could leave a puddle of water in bottom of pool (maybe 50 gallons) add a gallon of muriatic acid, and use a brush on a stick to wash down the pool. This acid is very toxic. Use gloves , rubber boots and goggles and rinse with clean water if you get any on your skin. If you are uncomfortable working with chemicals, you can hire a pool service company to acid wash the pool. They will use a stronger solution, which will remove alkalai buildup as well.