if it feels rough and tugs on the hair then its sharp
I know what you're talking about, but at that point, it's ALMOST sharp. A saw blade is rough and will tug on hair, but I'm sure you wouldn't call that "sharp".
A truly sharp blade will be extremely smooth because the two beveled edges will meet to make a perfectly smooth line. There will be zero roughness or drag, just a perfect edge that will slice through anything with barely any resistance. That's how a scalpel is sharpened.
When I get my knife to the rough, almost sharp stage, I switch to an Arkansas fine stone to put the final touch on it.
If you have good steel (probably not made in China), it should hold an edge through the entire field dressing process.
I also agree that a lightweight, inexpensive sharpener is a great asset to have in the field just in case you dull your blade somehow. It won't put a perfect edge on it, but it will be good enough to continue your work.