Troubles with interior paint

Hi there. I want to ask, why when I paint interiors, the painting from down raises with the second hand... I use Tamiya's Acrilic Paint before, but I don't like the results. So, I'm using now the Tamiya's Enamel colours... But the problem is there yet... For example, I'm painting the seats of my current S14 Autech Version with a comb. of Flat Red for the inner part, and Semi Gloss Black for the outter. The result of the red part is rough, with a strange shinning finish.
And, if I'm painting with gloss colour, what I have to do so that the result is smooth, without the brush marks?? :banghead: :banghead: :eek7: ........

Spray large areas instead of brush painting them

Use enamals as they take longer to dry therefore giving you more time to work with the paint.
Heat the bottle of paint in warm water first as this helps thin the paint down and makes it flow better.
If you are doing a fairly large area....put quite abit onto the brush and work quickly before it dries.
Use the correct brush size for the area. If you are doing a large area, use a bigger brush !!
Keep all the brush marks going one way and for the final finish... you should just use the weight of the brush to help smooth out the paint.
Try not to keep going over the same area as it becomes "tacky"..... as you will start to pull the paint off giving a rough finish.
Allow plenty of drying time(4-5 hours at a warm room temp) to put a second coat on if need.