Head doesn't seem right for mealy bug, but then there are many different species. I agree with above, soap is a good control for soft bodied insects, but doesn't really touch the hard shell ones like beetles. Ideally I'd use Safers Insecticidal Soap over dish soap as the concentration is standardized and doesn't contain the "extras" that come with many dishsoaps plus % active ingredient isn't standardized as with pesticide grade soap.
mealy bugs have a complex and difficult life cycle, you need regular repeated control measures to conquer them. Plus they hide in the soil, under the pot, etc. I agree also with above, if just one plant either throw it and the pot away or isolate this one completely different room from other plants....assuming indoor plants.