Suggestions,
1. make a short hose dedicated to drain the gray water. (if you have sewer hookup at your site, you may want to make an extension) Get a strainer for your sink drain.
2. get a 2-3 gallon container with a handle and cap, like some kitty litter comes in, and use it to collect the gray water.
3. You can carry or use a small luggage dolly to transport to proper disposal (dump station, pit toilet or even a flush toilet if you pour slowly) Sometimes a discrete nighttime disposal run is called for. :R
The secret is to generate small amounts of gray water. Don't run the water when rinsing dishes, brushing teeth, shaving, etc.
If you are really into water conservation (boondocking), you will recycle your gray water to flush you onboard toilet and convert it to black.
Hope this helps,