Do not use a fine grade paper followed by paint, the surface will be to smooth and the paint will not stick. As above, you need the clear to go on "wet" that is you need more.
If you are using pressure cans get a pot of hot water and sit the can in it for a few minutes to increase pressure, also when the paint is warmer it will change it's viscosity allowing it to flow better. good flow and atomization are critical.
If you like, rub the job back with say P400 wet and dry (With soapy water) just untill everything is dull, clean everything and then apply another coat of clear ensuring that you get an even layer of paint across the whole job, double check your work at different angles as this will help you notice areas that need more clear.
Oh and watch out for the edges on your job. They wont really need any rubbing back, just touch over them and thats it.