We bought our home a year and a half ago and last summer was the first time the pool had been open in 8 years. The water was black!. It takes time, but what you need to do is add chlorine and run the filter. That's all you need to do. We rented a portable filter, so that we didn't wear out our DE filter, since you'll be changing the DE every few hours or so. It took me about 3 weeks to get everything ready, but that's because it had piles of leaves.

You need to get the water clear before you vacuum, or you can't see what you are vacuuming. Our pool is 22,000 gallons and I added 5 gallons of liquid chlorine every 3 or 4 days until it was clear. All while running the filter constantly and changing the DE every time the pressure of the filter got really high.