I occasionally do, especially if it is going to be several days between dumps. I use a liquid and only put in about 1/2 the recommended amount, I also pour mine down the shower drain (rear bath) because it is the shortest distance to the tank. I don't recall the brand, but it is green and smells like sassafras
it is supposedly environmentally and septic friendly. FWIW when camping where it is allowed we prefer to let grey water run out on the ground, it doesn't really hurt anything in moderate amounts (in fact it is great for the gardens) and I only have a 10 gallon grey tank to begin with!
Aaron
