The Right paint

It sounds like you're not thinning your paint sufficiently or you're applying it way too heavily.

Though it will vary depending on the task at hand, generally speaking, when sufficiently thinned, your paint should be approximately the consistency of low-fat milk.

Don't get hung up on exact thinning ratios as they will vary from one manufacturer to another, vary between different colours from the one manufacturer's range and vary between production batches of the one colour.

well what company would give the smoothest results

This is really a matter of opinion and usually comes down to personal preference - I don't think there's a definitive answer.

It's funny. Paint brand is like a favourite beer brand or favourite car company.

There are a great many here who, like you, use Testors enamels and get great results.

Personally, my paint of choice is Tamiya acrylic, but that's not saying that it is better than another brand - it's just what I use and have become accustomed to using. 

It's a matter of learning how the paint behaves and knowing how to get the best results from it. This only comes with time and practice.