This is a semi follow up to my last post. Took apart the Shimano Nasci once more and after going through all parts, found that the oscillating slider was cast roughly on the inside hole that rides on the slide pin. I took some 1500 sandpaper and smoothed it out. But then I realized it may not be a bad idea to go over other friction parts of the oscillation mechanism with the sandpaper. All polishing described below done with 1500 grit sandpaper.

 

Oscillating slider 

1. Polish back (shown) to a shine

2. Wrap sandpaper around a tooth pick and polish hole that rides on the guide pin

3. Polish inside wavy area that the oscillating gear nub rides on

 

Oscillating gear

1. Polish face (shown) to a shine

2. Lightly polish inner hole 

 

This is a process I had never done before, and I probably should have taken pictures. 

 

Anyhow the difference is night and day even compared to other Nascis I own. I have supertuned (or tried) baitcasters before and never felt that it was worth the effort especially on $100+ reels. However, with spinning reels Shimano and Daiwa still typically use oscillating systems like the ones shown below and have lots of room for improvement. The sanding performed was minimal and I don't feel it should have significant, if any impact on wear (if I'm wrong, feel free to let me know). This is not a process I have heard of before and just wanted to share because the results were much better than expected. 

I know it’s just semantics, but technically Super Tuning refers only too baitcasters. As to your inquiry, polishing the sliding surfaces of your spinning reel is perfectly safe as long as common sense is applied. Meticulous cleaning and lubrication by itself may yield similar results. All depends on what you’re starting with.