Our new one never smells and the old one wasn't that bad either. I got into the habit of never putting any food stuff down it years ago. Give all plates a good wipe but if possible chuck the washing up water out the door anyway preferably over someones head or on their pitch.

If Im on some of our regular CL's with long scraggy grass Ill park near the hedge and just leave the tap open

Its only shower and washing water then really anyway. I couldn't get away with that on the posh shite in Devon though. Had to put it into a bucket and down the drain on our pitch or just wait until its raining at night and let it go.