First of all do not thin paint that much (what thinner are you using), that it will be like spraying water, you should try and thin paint 40/60 (approx) the later being thinner. Ensure that you have the right air pressure, pls do not ask me for the right psi because this depends on the consistency of your mix.
Then for spraying you start applying several coats, yes you need to re-spray on the same area but let the paint dry a bit before you apply the 2nd, 3rd, 4th.............coat, you have to continue going like this until you have an even colour all around.
Maybe if you use acrylics you find it easier to spray paint as this dries a lot faster than enamels so the chance of ending up with orange peel is very slim.
You can also use a small hairdryer to dry the paint between coats and so quicken the process.
I hope that you find this explanation useful, else if you still don't get it, we will try and do a demonsrtration at club.
If you end up with orange peel, you have to wet sand with a grade that conforms with the grade of orange peel, i.e. if the orange peel is deep you can start with grade 800 and then finish of with 1000 or 1200.