I have not personally used a kit, but I have held guns that had been coated.
As with painting, if you spray too much in one spot, yes it will run. Any coating will come off if you are too rough on it, some wear better than others. As far as peeling, if you do the prep work correctly, it should never peel or flake.... but the prep work has to be done correctly to remove all traces of dirt, rust, grit, powder residue, grease, solvents or gun lubricant.
You can buy the starter spray-gun (air brush style) which would help with the finer camo detailing areas and I believe there is a cure that you can spray on and harden it in an oven...
The best thing about using a DIY kit, you can personalize the finish to your liking.
Some of the newer Browning rifles come from the factory with the DuraCoat on them, they feel nice.