The Fels-Naptha bar grated up. One bar, on larger grate, created two cups.
The final mixture. I used the scoop from the oxy-cleaner. In the first load, I added two scoops to the wash, but realized that might be too much (not that it'll hurt anything) when the washer started the cycle, so I think one scoop will be plenty. This first load is mostly kid clothes, so if they come out clean and smelling fresh, we have a winner! All total, this cost me under 10, and aside from needed to buy another bar of soap when I run out, I still have most ALL of the ingredients left. So, this is a very effective way to save money.
Here is a helpful discussion of baking soda versus washing soda. I chose the baking soda because its what I had on hand. I will try the washing soda next time, I think, or do them both.
This website also has a dry recipe and it was the original one I was after, but Wal-Mart was out of the washing soda the day I was in town. So, I modified the two together, made a smaller batch from first listed websited but adding the Oxy-cleaner from the second website.
One thing I'll need to keep in mind, and both websites mentioned it, are the lack of suds. But, the first website goes into some detail as to how the suds are actually a cosmetic feature and really don't do anything to clean the clothes.