Best way to add high end sheen?

To begin with, your source has to generate those frequencies, and your modicum of capture has to support it. Vocals, a decent condenser mike, a short clean signal path to tape, in mono, sure. ITB or hardware synth...maybe, maybe not. If it isn't there to begin with, faking it with distortion or a severe EQ treatment probably isn't going to make you happy at the end.
 
Sheen is a pretty big word, but if you are looking at a spec analyzer I assume you mean exactly what you're asking for. Stand back and look at the entire process, from performance sourceS to your ears, receiving energy from your monitors. Ask yourself things like this:
 
1. What are my sheen options here?
 
2. Where do I want this sheen in the end?
 
3. Start to finish, what can possibly damage, counteract, mask, or otherwise step on my intended sheen? You may already have all you want, but by Fletcher Munson comparison, something you don't want sheeny is so sheeny that your intended sheen looks punk by comparison. In other words, make sure it's possible, and get the problems out of the way first. That's how you avoid painful sheen.
 
If you get thru all this, and it's there to begin with, just not strong enough where you want it, you have a TON of options. Look at them individually, because a great many of them may add broad sheen, while smearing localized sheenlet bands, and make things worse.
 
If you have waves five feet long, its going to take some significant phase delay to move the crests 2.5 feet in spacetime to make them cancel out, but that's thump, not sheen. Very slight phasing issues can cancel sheen. You can make this work FOR you as well because at high frequencies, phase summation lands very close to phase cancellation, selectivity is the key. If it stands out where you want it to with no downside, it's a win, no matter how you get there. Best to balance EQ without artifacts, though, simplest in the long run.
 
Options...including but not limited to, in my rough order of desirability:
 
Faders, Frequency Selective Cloning, Automation, Imaging, EQ cuts, Compression, Expansion, Modulation, Distortion, Reverb, EQ boosts,...but...best of all
 
Get it right on the way in, and never have to think about any repairs later. You need a wide arsenal of fixes in your pocket, artists are going to get tired, tight on money, tight on time. In rare situations, an after the fact repair is your only option.
 
But...I also do photography and the illustration is simpler. I can Photoshop the wrinkles off an old hag, AND fix the original lighting errors, AND rebalance the color temperature, AND sharpen the fuzz from cheap glass...
 
OR...
 
I can hire the right model to begin with, know my equipment well enough to choose the path to tech success (or buy/rent/borrow what the job requires).
 
Repairs can be adequate, but the image that sells is the one I never have to touch, that rocks from the beginning, and...it doesn't cost me hours and hours of tweaktime. In countless hours of attempted repair, I have NEVER been able to get "adequate" to match "brilliant from the gitgo".
 
The best I have accomplished, is to turn "marginal" into "adequate".
 
Strive for the brilliance.