I was stationed at Luke for about 7 years (lived in Glendale), so I can relate to the temps and hard water. :sun: More than likely, you received the recommendation to drain based on a high CYA (stabilizer) and/or high CH (calcium hardness). Those are two items that can only be lowered by exchanging water. Unfortunately, the products the pool store (and used by pool companies) increase those very levels. With TFP you won't have that happen again.
As for cleaning the pool, I wouldn't waste too much time. If you need to fill it, ... fill it. Once you have the water up to the skimmer, we'll show you how to add the proper amount of stabilizer (CYA) and FC (Free Chlorine/bleach) to keep the water clean. If there's a chance of residual algae in the pool/plumbing (which is very likely), we'll help you through a SLAM (link below) which is the process we use to eliminate algae. We'll also help you to adjust pH, TA, and CH as needed. All very easily done with the TF-100 and some local store products from a place like Wal-Mart.
If your pebbletech was only stained from the algae, don't pour acid on it. The bleach, once the pool is full again, will take care of that. If you have some other pebbletech concerns, let us know and we'll have a stone expert look at your concerns.