Thanks mate! Your guess was on the money; I printed it in ABS. Prior to painting I'd done pretty much as you suggested; I sanded it with 180 grit, then 400 grit, then 800 grit. The surface itself felt pretty good and close, I honestly think I got the finish I did either from the conditions (the day I painted was a touch on the cool side, with not much sunlight), botched painting with the rattle can (too much too quickly, holding the can too close, inconsistent resprays) or a combination of the above.
Spent a couple of hours the day before yesterday going over it with 2500 grit. Rinsed it thoroughly and left it to sit all of yesterday - partly because of bad weather for spray painting, partly because I was feeling particularly lazy (^_^') - then masked and repainted the gloss black today. I know the lighting conditions aren't exactly the same between the two photos, but the difference is already night & day! https://imgur.com/a/bj4WQbE
Planning to leave it overnight to ensure it fully dries, then I'll re-check. If it still needs a pick-me-up, I've got a high-gloss clear coat ( https://www.autobarn.com.au/di11064 ) to hit it with.