People have different methods, but I look under each leave, check every branch, & the trunk and kill it the same way you did in the first post. Then I'd spray down the tree with a home made insecticidal soap 2 times a week in case any eggs hatch. Spray the entire plant down from top to bottom, especially under the leaves. And separate the infected plant from the others.
You can also dip a cotton swab in rubbing alcohol and dab the alcohol over any scale you see.
Homemade soap recipe.
Pour 1-2 tablespoons of original Dawn dishwashing detergent and 1 tablespoon of vegetable oil in a gallon jug.
Slowly add water to fill the jug.
Pour part of this solution into a spray bottle and add 2 capfuls of rubbing alcohol.
Use immediately.
If there is any solution left in the spray bottle, add 2 more capfuls of alcohol the next time you want to spray your trees.
It seems that the contents of the gallon jug (soap and vegetable oil solution) can be stored for months without it going bad.
Spray on plants covering all leaf and stem surfaces.
You may have to spray from 3 - 4 times with intervals of 3 days.
Almost any kind of pest, including scale, can be eliminated using this solution.
It is not necessary to wash off the spray as no adverse reactions have been found.