First and foremost..... start with a sound source that is fat and full sounding.

Using the oscillators in a synth, either hardware based or emulated puts you at a disadvantage from square one. When you seriously listen to it, it might kinda sound like a horn, but on closer listen, no, not really.

There are plenty of sampled horn sounds and synths that use them. Many are fairly affordable and sound amazingly accurate to the instruments they are trying to emulate.

Compressing and doubling, while they are useful tools, still leave you with compressed and doubled synth sounds.

For a quick shot at horns where you're composing for fun, try the horn Real Tracks in Real Band. If using synths, keep them down in the mix and let the mix hide the fact that they're not real.

If you're composing for film and TV.... you better be using a really good sampled horn with articulations. Horn samplers can get pricey, especially the better ones.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.