What the fastest/easiest way to mass update all records to do a calculation?

I have an object that has 3 custom fields on it that are number fields. Based on the values of other dropdowns, I need it to update these fields. So for example, if Dropdown A has Value 1 then it should make field “Calculated Field A” 100, where as if it has Value 2 it should make it 50, and Value 3 makes it 0.

Then same with Dropdown B, if it has Value 1 then it should make “Calculated Field B” 50, and if it has Value 2 then it should make it 10, and so on.

I can easily do this via workflow, such as when changing one of the dropdown values, set the workflow to update the number field, but only when dropdown = a set value etc.

But how do I do it on all existing records? There’s about 3000 records today that already have all the dropdown’s populated. The only thing I need to do is add the calculated fields that hold the numbers. Not sure if I explained that properly, but I just need a workflow that runs and goes through every record updating the calculations.

I found this post here and was wondering if this is the direction I should be looking in: Bulk Data Edits

In general, it’s better to avoid having to do bulk operations, so if possible it would be best if you piggybacked on any existing workflow to do those updates.

If not, then do scheduled workflows on a thing that loops and feed it with a list of the thing you want it to loop on. On how to do this, search the forum, there are explanations on it already.