Testors makes acrylic water based paint and solvent based paint. First thing to check, if you're using solvent based paint, you need to thin it with paint thinner, water will not be effective. Second, assuming you are using water based acrylics, remember that Testors paint is designed to give good clean coats and coverage on model cars, planes, etc. not small miniatures with fine detail, so it may simply be unsuitable for the task of painting Warhammer model soldiers. There are other paint ranges that are as good as Citadel for miniatures, like Privateer Press and Vallejo, but they all cost about the same.