I taped it off to get the 2 tone going on I was after, modified the stickers to cover the join. About 6 coats I did to get depth, then applied stickers then I put 8 coats of clear TS-13 all over the stickers and everything for protection being a dirt bashing buggy it gets a bump and scrape here and there. It’s holding up well. Did that 10 years ago.
Depending on how deep the layer lines re give it a light sanding first, I usually use like 240 or 120 depending on how much needs to come off, then a coat of filler primer and another light sand just to get any last crevasses.
I you’re using paint like Rust-Oleum, that bonds to PLA just fine so doesn’t actually need a primer.
Looking at the image the slide and laser body look pretty decent so shouldn’t need that much, going perpendicular to the layers will take more off then just ease off the pressure to get a smoother finish.
That mount looks bad though on the top part, can see where the printer got some made wobbles or extrusion problems, can tell that was the bottom side too with excess brim, that can just be cut off with a blade.
The lines could do with a bit more sanding but there’s not much you can do about those chunky bits on the top, you could in use some modelers putty and fill them in and sand back but the marks might not be deep enough for that.
I’d be rubbing that back, the colour looks about right depends on the owner. Hit it with this stuff Tamiya 87044 Surface Primer 180ml Fine White Spray – Aussie Hobbies to fill the fine gaps, fine rub it again, apply colour 4-5 times or more until it looks right then lock it in with half a dozen coats of TS-13 clear for a bit of handling robustness. That’s what I’d do and call it a day. Up to you matey.