Paint Ridges

Even thin coats CAN leave a ridge.  I sand the result, after removing tape, with #1200 or even finer. It is amazing how fine a sandpaper you can get these days.  If you are sanding a gloss, you will then have to apply glosscoat, but I usually do anyway.  With a fine enough sandpaper you may get away without flat coating when doing flats.

One very labor-intensive method is to double mask so that you are putting down the same number of layers of each color.  Say you are putting down red and yellow.  After primer is done, mask off only yellow areas and spray N coats.  Then mask off yellow and spray red N coats.  Of course, each coat has to be put down the same thickness.  About the only time I do this is when spraying Alclad and some normal color paint.

The reasons for the ridges is clearly explained...too much paint along the masking edge.

Let the paint cure. Once cured wet sand with a little water and a polishing stick. Let the stick do the work, don't apply a lot of pressure. Gently reduce the ridge, constantly checking your progress by feeling it with your finger.

Rise and wipe down the model and allow to thoroughly dry.

As Bgrigg says, you are laying down too thick a coat.

In the past I have had some ridge / edge problems with camo paint jobs, to cure I left it until after the clear coat stage (Future) & then used some 1000 grit to remove the edge - using Future before dealing with it saved the colours interfering with each other.

Paint ridges along tape is caused by too much paint being laid down on each pass. Rattle cans are difficult to control! Lighter, and more, passes should work much better. Remember that spraying a heavy coat of paint is at 1:1 scale, and you're trying to create a paint job at a much smaller scale!

Also try to spray so that the air flows past the tape, rather that toward the tape. This helps prevent the tape from lifting, and building up a greater ridge of paint.