Will a clear coat smudge hand-painted details on an egg plane?

The bleeding problem mostly comes down to what kind of clear you use and how wet you apply it, not the curing time itself. Craft acrylics are the tricky part here because they stay soft for way longer than people think. They feel dry in an hour but they don't fully harden for a week or more. I'd give your blossoms at least four or five days, a full week if you can stand it, before any clear goes anywhere near them.

Second thing: keep it water-based. Solvent-based clears, the rattle-can lacquer and enamel type stuff, can actually soften or even wrinkle regular acrylic underneath, and that's when you get smearing and pulled lines. A water-based acrylic varnish won't bite into your petals at all once they've dried properly. On brush vs spray for something this small, I'd brush it. You have way more control over where the varnish goes, and you can keep it thin and out of the fine detail. The trick is thin coats. Get a cheap soft brush, load it with varnish, then wipe most of it back off so it barely wets the brush. One skim coat over everything, let it dry, repeat. Three or four thin coats will build up a nice protective layer without pooling in panel lines or swallowing your petals. If you go glossy it'll look like candy and the detail stays visible. If you want a softer finish, do two or three gloss coats first, then one light matte or satin at the end.

The fogging you mentioned happens when a coat goes on too heavy or in humid conditions, especially matte clears. Those have flattening agents in them that scatter light when they pile up. So whatever you use, multiple thin passes, decent ventilation, not a freezing cold or damp day.

Before you commit to the actual model, test the whole process on something disposable. Paint some white over pink on a plastic spoon or a bit of sprue with the same brush technique, let it cure a few days, clear it the same way. If the lines stay crisp you're good to go, and you'll have way more confidence when the brush touches the real thing.

One thing I learned the hard way on a hand-painted figure: brush-on varnish loves to wick into seams and recessed detail, so on an egg plane that means the canopy joint and any panel grooves will pull more than the flat surfaces. I keep a clean brush with no varnish on it at all and just touch it to any pool that starts gathering, it soaks the excess right up before it dries in a blob. Also, do the petals a favor and check your water, I once used water straight from the tap that was apparantly harder than I thought and got a faint white film over some pale yellow. Distilled in a little jar fixed that entirely.

Still finding my feet around here but this thread is helping me too. I hand painted some small details on a little tugboat kit a while back and the one thing that got me was handling it during the curing wait. The paint felt dry so I picked it up to admire it and left a fingerprint squished into one of the stripes. Ended up having to touch it up and wait all over again. So if you do wait that week like people are saying, maybe handle it by the stand or wear cotton gloves, or at least only grab it somewhere you coud easily fix.

Also curious, does the egg plane kit come with a clear canopy piece? Wondering how you'd mask around that with the varnish without gumming it up.

Update: it worked! Waited a full week like the first reply said about craft acrylics staying soft way longer than they feel, and that was definitly the right call. Also took the tugboat poster's advice to heart and barely touched the thing during the wait, no fingerprints this time. Ended up spraying a few light coats instead of brushing, so no wicking into the panel lines and the blossoms stayed crisp. No fog either, so the thin layers thing was real.