This isn't homemade, but it stretches your softener. Get a 5 gallon bucket with a lid and add to it:
1 large bottle of fabric softener
2 bottles (use fabric softener bottle) water
4 all purpose sponges cut in 1/2
Stir the ingredients together and when you add a load of clothes to your dryer, squeeze out 1 piece of sponge and add it to your load.After the load is dry, replace the sponge in the softener. This stretches your softener 3 times as long.