Stumbling Slant --what is left??

With ATF, flooding the engine to a stall is not required, nor is letting it sit overnight, as there is no chemical action taking place. There are better chemicals available.
I have had good results even with water, which, in the chamber converts to steam, rather explosively, at a very-hi idle and does a great job. Just don't feed it too much too fast, no big deal. With water you don't need to bop the valves they will be clean as clean can be. What I do is get a kitchen atomizer and blast the primaries.

To Bop the valves, Here is what I recommend for a first-timer.
remove the rocker shaft.
install a LeakDown tester set to ~90psi, (yes you can use less but there is no need to go higher) and slowly pressurize, blowing the piston down to the bottom. Now you are set. I use a small hammer. The trick is NOT to hammer the valve.
The trick is to bop it such a manner that the hammer slides off the stem, and let the combination of air pressure and spring, slap the valve back onto the seat, crushing any carbon that might be there. You only need to bop it say .25 inch Two or three shots will blow the carbon off, and the sound will change to a deeper-sounding thunk, and the hissing of the escaping pressure will cease.
If it does not, and they all sound the same, then either;
1) this was a colossal waste of time, or
2) your intake valves are all bent or
3) your exhaust valves are all burned.
Next is a proper LeakDown test, which, with the Rocker shaft off is so simple.
Just crank the pressure to 90psi and blow the piston to the bottom then read the % leakage. This tests the valves, more so than the rings. After all six are done interpret the results. If all are similar, then yur done. But if some are quite a bit higher than others, then something is up. At that point, you need to squirt a little oil into the cylinders with low readings, to test the rings. After the oil goes in, (about a tablespoon), you need to crank the engine a bit to distribute it around the ring. Then reduce the test pressure to 30psi, and hit the LD tester, while watching the gauge. The number should, initially, be higher, then drop as the air pressure pumps the oil into the crankcase thru the ring gaps. or other gaps, lol. If it does not act like this, you will need to listen at the carb or at the tailpipe for hissing, which would point to a leaking valve(s). If you hear it in the CC, the engine s sorta doomed at 90psi cranking compression. Well if it hisses anywhere but into the CC it is doomed anyway. Some hissing into the CC is normal, but it cannot begin until AFTER the pressure is turned on and the previously injected oil is blown down.
IMO, and others may argue,
as for ring leakage only, exclusive of hissing valves, at a test pressure of 90psi which is what I use;
less than 4% leakage is pretty good.
over 10%, she's getting lazy, and seems to be using a lotta gasoline especially around town
over 20% she's a turd in desperate need of attention. Sure it runs. Sure it smokes. Sure it fouls the plugs. and sure it gets lousy fuel economy; but it still runs.

Happy Easter