Defects
You are bound to get defects in your coatings. If they come from the coating method itself then you will be alert to TopCoat's warnings in red and may well be able to root-cause fix them. But many defects aren't directly related to the coating method. TopCoat can help you with these, too.
The Defects section discusses the problems of levelling of uneven coatings, Holes, Ribbing, Runback, Air and Bubbles. What follows is an example of the Holes tool to show you how insightful TopCoat can be. 
There's a formula telling you whether a hole (from dirt or air) in a coating will spontaneously heal itself (which is what you want) or continue to grow (which is what you fear). The formula is simple enough but a visualisation of the formula seems to be helpful for exploring how resistant your coating might be.
Here's a typical example. You have a 150µm (6mil) coating and by chance a 0.2mm hole appears from some contamination. The good news is that if the contact angle of the liquid with the base is 50º (or less) then the hole will spontaneously shrink and your coating will be perfect.
But here's the problem. Next month you decide to coat the product a little thinner - 140µm. You happen to have the same level of defect-inducing things on your machine, but this time your holes spontaneously grow and leave you with a visible defect. You naturally think that there's some extra contamination ("oil" is always the favourite) in the machine, but all that's happened is that thinner coatings more readily open up into permanent defects.
What can you do about it? If you change the substrate so that the contact angle is 40º then you find that you need to go down to a thickness of 90µm before the holes grow:
So, in this case, a small change to your substrate could be a big change in your chances of producing defect-free coatings.
Would you have been able to work all that out just from looking at a formula? Probably not, but if you are good with formulae then one of the handy things about TopCoat is that at a click of the Fx button, the formulae appear:
