We also used Vinegar for the softener. The mixture we used was: 1 gallon of White Vinegar, 1 tbsp. of vegetable based glycerin, & 10 drops of Lavender Essential Oil. If you buy a gallon of White Vinegar, you can just dump the other 2 ingredients right in the Vinegar bottle. And, you can use whichever Essential Oil scent you like. You really can't smell it much when the clothes are dry anyway. And I promise you can't smell the vinegar!
We just put it in our Downy ball like we normally do with fabric softener. Then, when we threw the clothes in the dryer, we tossed in those little rubber balls that bounce around and help prevent static cling and also help soften the clothes (We have the ones that are made for that specifically but I know people who use tennis balls for the same thing. It doesn't matter which you use).
So, 1st experiment was successful and we look forward to our next product!!
M&K