If you are doing the experiment as your first time, for practice also, try something with edges. Flat surfaces are far easier. The corners are where you are likely to burn through. Maple and Cherry are completely different. Cherry is open enough to definitely need a filler. Maple is more closed, a filler is not as necessary, though with just a little time pssage, the structure of the wood will telegraph through the lacquer much more than if an epoxy filler/ sealer is used. . Mahogany would be a good practice wood, if Koa is not an option. Koa will be very different than Cherry.
Sounds like you are working toward a full polished lacquer finish? If so, my 2 cents say, spray carefully, make sure the corners are coated sufficiently. The epoxy fill coat needs to be perfect, what you leave there is what you will end with, essentially. Sand it carefully, and fully 'flat'. When doing the final 'flat' sanding of the finishing prior to buffing, treat every sanding stroke as a 'cut', in other words, be careful and patient. Time spent earlier in the finishing process, getting things right, is more efficient than trying to fix issues it the final stages. Take the time to be sure your edges are 'broken' exactly as you like at finish, prior to the epoxy filler, and zero flaws in the wood.
If the lacquer is not laying flat easily, either adjust the fluid needle more open, add thinner (acetone) or both. If lacquer is building too quickly, reduce the fluid. Watch buildup on the air nozzle, this can also impair layout, though on a single uke, buildup should not be an issue. The orifices on the air nozzle are precision, caution with metal in this area... Strain your lacquer always unless you are ok with the possibility of fluid born contaminants. Be aware of ALL temperatures, and relative humidity.