Painting window sills with w/b gloss

Anyone got any tips on how to do this better?

I'm fine with doors and frames but I undercoated a window sill yesterday and was not impressed with my efforts. Lots of brushmarks. I found it tricky to lay-off on a flat surface. I know one mistake I made was to do this when the sun was streaming through the window thus making the paint dry quicker than is ideal so will be doing it next time when the sun is off the window sill.

If it makes any difference I'm using Johnstone's Aqua and Purdy brushes.

Thanks.

Exact same as I did.

Basically i got one of those mini foam rollers & did it like that. I found the paint dried out too quickly by brush & i didn't want to smother it, so i rollered it & then laid off. Sure a professional would've no doubt got less brush strokes left than i did but i got way less than i did when going totally by brush & at any rate, i was satisfied with the end result which is all that matters.

Couple of things help. Dampen the brush and the sill and you can very slightly thin the paint with clean cold water. Work quickly and don't muck about with it, lay it of lightly once or twice, don't play with it. Abrade lightly between coats but be sure to dust off. I've found the Dulux QD undercoat and gloss to be the best. Also wash the brush out regularly.

I personally did all of the above ^^

I was/am a total novice with this water based stuff though & for large flat areas i found the roller method the easiest by far. I'm not saying it's the best method, just what i found easiest.