Yes, I think the main variation in your method is that you have the solution much hotter than most of us.

The fizzing is when the sodium bicarbonate breaks down into sodium carbonate (washing soda also known as soda crystals), and carbon dioxide gas. This is the gas you find in carbonated drinks.

The upshot is that for along time, I have used soda crystals, as you get more for your bucks. I would also caution about using this solution when there are stones which have been oiled or waxed, because this solution is ideal for degreasing, leaving the stones dull and whitish. The process is of course accelerated by heat.

Welcome to the forum, Dennis.