Painting - where have I gone wrong?

[andysea]

Hi folks
Background - redecorating my home office. Previous paint I believe was standard emulsion.
To prep, I did a light sanding down with very fine sandpaper, then washed the walls.
I've started to cut in today with vinyl matt and as you can see, it just looks awful - hopefully the photos explain but it's like this majorly streaky effect.
The photo with the two bits of grey/blue colour I'm using and the white is where I was wondering if I hadn't rinsed the wall off enough. Here I've taken a patch, re-rinsed and dried. Same result.
Brushes are new, paint is brand new. I've tried putting a bit of white up to see if a different paint had the same effect - I think is slightly better.

Where have I gone wrong - prep or paint?
thanks!

 

[foxhole]

Have never sanded or washed walls prior to painting, were they dirty ?
Did you stir paint?
Why masking tape?
Why not roller it ?

 

[opps]

Sorry, I am a tad lost. Are you covering the room colour with the new, darker colour? It doesn't look like you are. I looks like you painted over a white paint. Regardless, you need to let the paint dry for about 4 hours before applying the next coat. Recoat too quickly and you risk pulling off the previous paint.

On the balance of probability 3 or 4 coats of your paint will suffice. A lot depends on the quality of the paint, and the quality of the brush. I pay £18 to £25 for each of my brushes but as @foxhole seems to be suggesting, a roller would have probably applied the paint more evenly. Try one and see how you get on.

Edit-------- sorry, I now realise that it is just the window reveal that you have painted thus far. Looking at the sample of white paint, those brush strokes (aka tramlines are very heavy). Which brush are you using?

 

[robinbanks]

You've masked; do it all with a roller (or dappled brush action in the very-corners) to prevent streaky brush marks.

What paint (brand/model) are you using?