Here's what I do.  I buy that orange stuff hand cleaner without the pumice.  I 'pre-treat' the heavy areas, and then throw the clothes in a 5 gallon bucket I keep in the barn... I use this bucket just for 'farm laundry'.  I then add water and simple green degreaser.  I slosh it around with a broom handle.. let it set for a few hourse.. remove, and hang onthe fence, and spray rinse, and let dry.
I learned early on that I wasn't sopposed to wash greasy stuff in the house....how did I learn this you ask?
Lets just say, the wife came home one day and i had the front grill to my 8n in the sink scrubbing it down prior to painting it one day.... not a pretty site....
Soundguy