I found that MEK is only partially miscible with water. I hadn't read about that before so I've been using acetone until now, which is 100% water miscible so can't be separated easily. Amyl alcohol is also even less miscible but not as common to find in a store and slower to evaporate.
So the trick that this MEK miscibility opens the possibility of is getting rid of most of the MEK and thereby concentrating the extract into a smaller volume of solvent to be evaporated while at the same time washing out water solubles. Water can dissolve almost 30% of an equal volume of MEK, and the MEK only dissolves about 12% of the water. So if you add twice the volume of water you would reduce the volume of MEK by almost two thirds. You can add as much water as needed to get the MEK volume down as far as you want as long as it still is thin enough to be able to conveniently separate it from the water layer.
So once you separate the layers the MEK with the extract it will have about 12% water in it which needs to be removed. To do that, I intend to use magnesium sulfate, epsom salt. Maybe silica gel or calcium chloride, though the latter is supposedly dangerous to the lungs if dust is inhaled so I'll try others first. Then with the water removed it's a simple evaporation with purge. MEK is not very dangerous to health anyway. It's naturally present in many plant materials, like coffee beans. Any residue would likely be harmless though you would want to get it to as low a level as possible to avoid tasting or smelling it. Actually I could just not bother removing the water and just let it evaporate too, or pour it off if it's that much.
The main point of the MEK is to be able to simply wash out most of the solvent with water and also most of the water solubles. You could wash the solubles out of any alkane like hexane, but you couldn't wash out most of the hexane itself and thereby concentrate it. You'd still have to evaporate a large volume.
I haven't actually done any of the above yet. Just bought a can of MEK for my next extraction when the time comes. It should work though. Couldn't be worse than the acetone extract, which admittedly is pretty harsh. I'm hoping the water washing helps with that some.