After you clean it by hand are you also changing the soil? Also, for scales triple check the roots for shells as well since these types of pests are drawn to new growth which can include new rooting. Mealies are also attracted to new growth but tend to shake off the roots when the plant is uprooted. Cyms have alot of nooks and crannies In the leaves which can make these a little more complicated to hand clean. If you have a good area of air circulation where the plant can dry out I would reccommend soaking your plant in warm soapy water in order to get into the crevices but again ONLY if you have a way to dry them out afterward. Soak about 2-3 minutes. The ones that dont drown will move their way up the leaves to get out of the water where you would be able to better see them to remove them. They are slow movers so give this some time. Make sure to dry the plant completely to avoid rot.