for the prop_anim_ratio, you may have to adjust to probably get the efect you want.

Adjusting the rotation of the propellers is a two step process - in the visual model, you reverse the axis (so the "Z" axis point to the rear, AND to get the flight dynamics effect, you adjust the entry in the cfg file  (check the makemdl SDK for the specifics...  I Don't have it handy right now.)

Ajver. I've reversed the prop animation on several of my own aircraft with no problem. Felix knows a lot more than me on this stuff but I don't remember reversing the Z axis.
This is the Aircraft.cfg [propeller] entry I use for a single engined aircraft.
rotation= -1
For a twin with both props reversed use this.
rotation= -1,-1
I assume an aircraft like the P-38 with different rotation on each prop would use something like this.
rotation= 1,-1

I'm sure Felix will correct me if I have the wrong idea. It might not be possible to do as you want in either FSDS2 or Gmax. Both use the animation naming conventions described in the FS2002 MakeMDL SDK. These are generally so much better if not so adaptable as some AA features.
I think the propx_slow variable is visible during startup or shutdown only. This gives a smooth transition from the stationary to spinning prop. It's a matter of preference but using the 3d stationary prop instead of a segmented transparent disk for the _slow part of the sequence suits me better.

Hi Ajver. I think the default prop animation is set up for a 3 bladed prop. I assume this would be defined as prop_anim_ratio=1.0. The visual effect might also vary depending on the max rpm & other AIR file/Aircraft.cfg variables.
I have found that prop_anim_ratio=1.48 works well so far for my CFS2 aircraft with 4-bladed props.

I must confess that I haven't read Doc's tute yet. All this is based on advice from other designers & my own experiments in FSDS2.

Well, I think you will always get this effect. The prop disk will start rotating in the "correct" direction, then as the revs increase it will pause before appearing to rotate the other way. The opposite happens when you reduce revs & the idea is to get it to work smoothly without freezing at a particular power setting, usually full power. It's the same optical illusion you get with spoked wagon wheels in old Western movies.