Help with streaky paintjob

Hi all. I've recently painted our bathroom door and the brushmarks are very pronounced. I applied one coat of 3 in 1 sealer and three coats of mould resistant bathroom semi-gloss acrylic. I painted the door outside in the sun, but it was a very cold day (5-10 degrees). I tried the last coat inside where it was 20 degrees but that's no better.

The problem is I intend to paint the walls and roof of the bathroom with the same stuff and I don't want the same crappy finish. Any ideas on what I'm doing wrong?

Thanks, Brett


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