[Jay!]

What type of paint are you using?

Brush strokes are from brushing over paint that's already starting to dry.

Enamel paint works best with brush painting, because it dries the slowest, so it has the longest time to level off before it dries.

Adding more thinner might help give you more working time. But, you'll have to put on more coats, since the paint will be thinner, and you'll have to wait for each coat to cure before doing the next...