My basic approach is to name the most skilled dwarf of each important profession the "Chief XYZ", for example "Chief Weaponsmith", if a new immigrant comes along who out-skills the old chief, or if a dwarf moods their way to legendary, then I rename the dwarves to make the new one chief. I then make extensive use of workshop profiles, usually I'll create specialist workshops which only have the relevant chief or chiefs assigned, or I'll use minimum/maximum skill levels, depending on what's appropriate. Having a chief is useful even for jobs like furnace operating, for example if you have one highly skilled furnance operator, and a bunch of low skilled ones, it can be useful to have one furnace set aside for the highly skilled one, so that you don't get the scenario where the low skilled dwarves hog all the furnaces, leaving nowhere for the skilled guy to work. It's the same with say, masonry and block production - sure, anyone can make blocks just fine, but a legendary does it soooo much faster, so you want to set aside a place for them to work.
I find that I don't really need to use Dwarf Therapist, unless I decide I need a dwarf with a certain profession, like say, a leatherworker, and I can't remember which if any came with that skill. That's when DT is useful for tracking down the most skilled dwarf so I can put them to work.
I also sometimes rename a dwarf's profession to their highest useful profession, for example if I get a high master fish cleaner / proficient carpenter, I might just rename it's profession to Carpenter.