Insecticide for umbrella plant- how long for results?

Hello! I noticed scales on my umbrella tree last week and spent a looooong time cleaning each leaf/stem with isopropyl alcohol, on Sunday I applied imidacloprid insecticide granules (watered into the dirt) and sprayed it with neem oil. Today I noticed a bunch more scales on my plant :( does anyone know how long until I should see results from the insecticide? And if/when I should re-apply it?