My daughter is currently using the Aveeno Baby Wash and Shampoo product. Compared to other brands like Johnson & Johnson, Aveeno is a bit costly. Her skin is fine with the Johnson & Johnson wash products, but sometimes, we grab the Aveeno brand from the grocery shelf.
Lately, I discovered how not to waste the baby wash by using the empty bottle of the Johnson & Johnson foaming wash. Instead of pouring the shampoo directly on my hand and rub it all over my daughter, I pour out a small amount in the empty bottle and mix it with water. Measurement would be 1/4 shampoo and 3/4 water (using the empty bottle as the measuring tool). Using this technique, we save a lot of the shampoo. We didn't have to buy another one too soon because we still have more left to use. The same thing should apply with other brands of baby wash. Whatever empty bottle of foaming wash available to you (as long as it's refillable), you can use it.