What gives more sharper reflections in Clear Poly? Brush or Spray Gun?

[Tegmark]

Doing some samples with brush, straight out of can vs. thinned at 5%, 10% 20%. Thinning ruins the sharpness & the look is bad imo.

Does this happen with good spray setups? I suspect a good brush with thick clear cant be beat for that ultra sharp mirror finish.

If any sprayers can please tell me.

[Master Splinter]

Two-pac automotive poly off a good, well set up spray gun will give you the best gloss-off-the-gun finish. After it has hardened, cutting with 1,500 and 2,000 grit and compounding can give you whatever level of higher gloss you want.

See this from about 10 minutes in.
1K Acrylic VS 2 Pack Auto Paint + Dent Repair - YouTube

[Robson Valley]

I suggest that you might be able to do either.
Provided:
1. That the temp is cold enough so that the finish can flow before the solvent evaporates.

I brush-painted a couple of spare sets of truck rims from the wrecking yard. One day was maybe 25C, worked in the shade, every brush stroke showed on one set. Early next morning, temp no more than 15C and it didn't warm up, the paint flowed like magic, like it had been sprayed. Sure, took ages to set up.

2. Calm air so the solvent "hangs" for the flow time. Had to paint some studio photog gear with black.
Windy paint booth, brush marks. Cut the air flow to minimum for 30 minutes = lovely.

[rod1949]

Spray over brush any day.

[nrb]

Have you tried using a small foam roller?