The method stated is indeed the best method, if the tank is removable. Often it is not. Then one looks for alternatives.
Check if your area has a fuel polishing service. They drive over in a boat equipped with pumps and filters. Cost varies depending on access or what they have to do to get their wand into the tank. There is a crud that builds up on the bottom of the tank from dead algae that needs to be broken loose, pumped out and filtered. The clean fuel is then pumped back into your tank. Once it is scraped clean they will keep recycling the fuel until it is clean. Process works good if the person knows what they are doing.
I did this myself rather than paying someone else to do it. My problem started when the pick up tube in the tank was plugged by some loose crud. I removed the fuel gage sender which happened to be over the lowest part in the tank, good thing because this is where the crud is. I scraped the bottom with a copper tube as I pumped the fuel through it and into a makeshift filter made out of old t-shirts and gallon plastic jugs. Once filtered I poured the clean fuel back into the tank. I used an outboard bulb pump which worked fine, just tiresome and slow. This is somewhat dangerous, very messy, smelly and pretty unpleasant. It was however dirt cheap.
My engine was set up with 2 in-line filters, a Racor and the one that is mounted on the engine. I used a 30micron for the Racor primary. After this process I had no problems more problems, 5 years then sold the boat.
Now that I have had the experience I would hire it done.