Angle grinder + flap disc + nail in the wall/workbench for balancing + 1 minute of your time = all you need
Before I finished building my reel mower, this is how I maintained a razor sharp blade on my rotary mower before every mow (2x/week) with low cut turf. It is definitely much less of a PITA with an electric mower since it’s so easy to prop it up to zip the blade off being that there’s no fuel spilling to be mindful of.
Where I’m going with this is, you don’t need anything fancy or ultra precise to get a proper sharp mower blade that delivers excellent results (for a rotary mower). And you definitely don’t need to be a nut and sharpen it for every mow, 2x/season is probably fine for most people. Just follow the existing angle with a few passes until it feels sharp (scientific, I know), repeat on the other side accordingly, hang it on the nail to see if it’s visually level (i.e. pretty good is good enough), and go from there.
Remember: 1) a blade tuned up this way without expensive/precision gear is a 1000x better than a dull factory edge blade, and 2) replacements do exist and they’re relatively cheap — you don’t have a whole heck of a lot to lose…
…oh and 3) it’s just grass

Don’t sweat it. Good luck
