I just use equal parts borax and baking soda, and it works pretty well.  I hadn't heard of adding salt and lemonade, but that sounds good.  One of my friends squeezes a lemon into the place where you put the dishwashing soap sometimes and says that's supposed to help it rinse better.  Mine rinses just fine, though, although I think it would make it all smell good.  :)

I tried a recipe from tipnut but I tweaked it a bit. I use 1c.borax, 1c. washing soda, 1c. kosher salt and 1/4 cup citric acid. You can use two envelopes of lemon kool-aid, unsweetened, in the place of the citric acid. It works great for my hard water and I use plain vinegar in the rinse instead of that blue jet dry stuff. I keep it in an old tupperware container under the sink and it is cheap to make and works great

I wonder if you could add some boiling distilled water to the powder and use it that way. I know that borax won't dissolve unless the water is very hot. I put my water heater on high 30 minutes before doing any washing because I was fed up with the not cleaning of the tepid water. Funny how a little thing like water temp changes things.