Follow the yeast washing steps, but simplify. If your current beer is relatively mild, no super spices or hops or dark grains, then the yeast cake should be neutral.
- Boil a canning jar of water, sanitizing the jar & lid.
Cool the water to the temp that the yeast is at.
Rack the current beer off.
Dump the water in and swish around.
Dump the slurry into the jar.
Clean the jar opening & cover it.
Put in fridge until brew day.
That's what I am about to do tomorrow as I leave for a week and can't brew the next beer in the series until I return.