Ah, I see you did go down the custom route.

There are a wide choice of clearcoats you can use, especially if you are keeping it all natural, and yes, it comes in aerosol form. You've got a choice between polyurethane, acrylic and nitrocellulose clearcoats.

Nitro is the classic finish, but it's expensive compared to the others and the solvents used are nasty, so a solvent mask is required when using it. But it is generally considered to be the finish that ages and wears best (in terms of looks).

Polyurethane is a tough protective finish, and a lot of guitars (e.g. almost all Fenders) come finished in polyurethane. The only downside is that being harder, it does tend to chip on contact rather than simply leave a mark.

Acrylic is what's in standard car spray paint cans these days. It can be a bit slow to dry thoroughly at times, so thin coats and leave plenty of time between coats. Too many coats too quickly and the lower coats are still wet when the outer coat is dry and this really slows the drying process down.

All will give you a nice finish, and all of them will require rubbing down with sandpaper to get a flat finish which you then polish up again (you won't get anything like as nice a finish if you just spray and leave it). You don't want too thick a finish, as this can kill body resonance, but you do need to put on enough coats to give you the depth to sand down for polishing without sanding back to the wood. Any spraying really needs a suitable mask, but it's most important with Nitrocellulose, which does need a mask with a HEPA and carbon filter built-in. If you can smell the spray whilst wearing it, then it's not fitted properly or the carbon filter is worn out and you need a new filter.

Mahogany is an open-pored wood, so will need grain filling before the clear coat goes on. You can leave it unfilled, but it will take an awful lot of spray to fill up all the pores, or else you get a very rough finish. So I'd use a water-based grain filler like Timbermate on the mahogany. You van use a mahogany colour if you want the filler to blend in, or a darker colour if you want to highlight the grain pattern.

The spalted maple veneer is a closed-grain wood, so doesn't need filling. Only sand with a very fine grit, say P1500 as the veneer is very thin.

Even though you are not staining and just going for a sprayed clearcoat, I'd still check it thoroughly for glue spots as they may show up as lighter areas under the clearcoat.