I would not expect pesticide treatment to resolve the scale problem the way it looks now. The systemic product works best for prevention, not cure. Try removing the bugs mechanically first. Wipe the bugs with rubbing alcohol first to loosen their grip, then remove them with a Q tip or similar. Once they are detached they are basically done. You can come back for a second round of cleaning in a few weeks if the problem isn't solved right away.
Of course everyone should choose the best route for them, but I see a couple problems with using pesticides where they aren't needed. First off the 3 in 1 is overkill, and not in a good way... a simple systemic insect control product accomplishes the same goal with less chemicals being put into the world. If you don't have a mite problem, why use an acaricide? Second the use of pesticides is not necessary or even helpful for the vast majority of succulents I grow. When you treat everything in the garden, you are basically guaranteeing the absence of beneficial insects.
