Naphtha, naphtha, naphtha. Sorry, spelling police here. No one ever spells it right.
That being said, forget about that, and use 91% rubbing alcohol and gauze pads or
cheesecloth. If you have some really ground in dirt or swirl marks, use melamine foam
pads (like Magic Eraser) along with the alcohol. Rub gently, as excessive use can get through
the paint and into the wood. The fumes from the alcohol are not nearly as bad as those from
Naphtha, and it's probably cheaper as well. Keep wiping the playfield down with the alcohol, until
it's totally clean and free of dissolved wax residue. Then use Novus 2, followed by a good carnauba
wax, like Mother's (in the bright red tin). Your playfield will gleam.
"Hi-Lo Ace" is a fun game, but dirty, non-working and with a broken backglass, it's probably like a $150
game. Unfortunately, that backglass was not reproduced by any of the major players, but you could
go with a BG Resto copy (bgresto.com). I'm not sure if they have the art file for that glass, so you may
need to send them yours in order for them to make a repro.

I've seen a couple of them for sale at shows. There was a pretty decent one that went dirt cheap at the one and only Ohio show I ever attended (the one in Niles a few years ago). There was a very nice one for free play and sale at the York show a couple of years ago.
Compare the playfield layout to Gottlieb's "Bank A Ball"/"Flipper Pool". There's a fourth bumper on "Hi-Lo Ace", but otherwise they're very similar.

That's a very sound strategy for a player's quality game that you want to clean up, and make presentable.
I can tell you have a healthy passion for this game, being your first EM. It won't be long before you bring in another, then another......

Why would alcohol affect the clear and not the colored layers below? If what you're saying is true, the clear is what's holding much of the dirt, being that it's the upper layer. If it's dirty, and likely compromised to begin with (I don't think it's very thick), it's probably better to remove it, and protect the remaining artwork with several coats of wax and a new ball. For home use, this should preserve the playing surface indefinitely, as long as it's waxed periodically.

Something to consider then. I would guess then, that using an abrasive such as a Magic Eraser with anything as a wetting agent would also remove any remaining clearcoat, correct?
I have used naphtha (Coleman fuel), and even charcoal lighter fluid to clean playfields, but it usually doesn't get the surface very clean.
I try to tailor my approach to the type of schmutz on the playfield, the condition of the surface, etc.
The least aggressive method is always the way to go, but as you've said, it all depends how clean you want it to be versus long term durability.