I have been decorating for thirty years and in that time I have seen a lot of acrylic gloss paints and honestly hand on heart I think Dulux Trade Ecosure Gloss & Undercoat is the best. Not only for the gloss level, with one coat a nice level of gloss is achieved and with more applications a higher gloss can be achieved.
This surface has just had one undercoat on, If you have brush marks in your undercoat then they are going to come through to the gloss so you may need to give the surface a bit of a rub down.
This is the biggest tip you will get for applying gloss:
When using a good quality synthetic brush just dampen with water this will prevent the brush from clogging up and leaving brush marks.
Again you will notice the different between acrylics and solvent based paints, you can apply acrylic a lot heavier than a normal undercoat. It does flow out and it does actually go much heavier. If you get it on and lay it off ten minutes later particularly if it's a colour. Then you can get a flash and it will look like two different colours because you are flipping the pigment. So the best way is to get it on the surface lay it off and leave it.
Apply lots to the surface and once on, just like any acrylic even it out. As long as you have an even coating to a degree it will not run. Then using the bristles of your brush lay it off to ensure a nice even coating.
Dampen a large brush again and also lightly dampen the surface to paint with a ringed out sponge. Apply lots to the surface and once on, just like any acrylic even it out. As long as you have an even coating to a degree it will not run. Then using the bristles of your brush lay it off to ensure a nice even coating.