Use gray to flush black

When our gray water tank starts to get full, we open the valve and drain some gray water into a bucket and then pour the bucket into the toilet. Both the gray and black tanks are 25 gallon, but we generate about 5 gallons of gray water a day and maybe one or two of black water. So this "bucket brigade" helps extend the time that we can boondock, and it also dilutes the black water.

A pump would be very useful, but I am not sure how to plumb it safely.

Run the water that you waste to warm up the shower into a bucket and use that. I would use the gray water. I have a clear section of sewer pipe and the first glug of gray water is pretty nasty with solids and coffee grounds.

I pour dishwater down the toilet.

I would suggest that you find a flat pan and collect the shower water as you stand in the pan. Some might miss it's mark, but pour that into buckets, maybe through a strainer to collect the hair. There is small lines and valves that water has to flow through, and the use of gray water as a flusher could lead to a lot of problems if something that went into a gray tank gets stuck along it's path, or causes gate valve problems in the toilet.