Howdy,
It really depends on how much you put in, and how you put it in. You can remove the top panel, remove the muffler, place a bunch of rags and such around the exhaust manifold. Start with hand turning to see what you can get out. Connect the batteries and use the dead crank at short intervals. Like crank for 2-3 seconds, wait a while and crank again. Then put your muffler back on.
Not the same as you, but my MEP-803A showed signs of severe wet stacking, I removed my muffler, and the exhaust manifold. I then pressure washed all the crap out of the exhaust manifold. I then used screw drivers and knives to clean out the black goo. Shop vac the last little bit. Put it all back together and fired it up and put a load on it, which really finished cleaning it out. Black rain.
Since you have the marvels mystery oil, you could also prime it thru the fuel system to make sure things are lubed up.
Batteries = Most of the Optima batteries will come back to life. It takes some time. Put it on a charger conditioner which has a AGM mode and let it sit and do its thing. Might even take a day or two or three.