For me, the trick to managing labor without Therapist is to process migrants as they arrive. I used to make notes on every arriving dwarf. For example, here are some migrants who arrived at the offshore platform I was building a while ago:
Minkot Shedimîton, miner
almost never sick, very slow to tire, very strong, clumsy, very slow to heal
great sense of empathy, good creativity, questionable spatial sense, very bad
intuition
quick to anger, occasionally overindulges, confident under pressure, often
cheerful, candid and sincere, immodest, confident
Assigned: mining, architecture, mason, potash maker
Note: could become a weaver
Onol Bufutcatten, woodcutter
quite quick to heal, strong
very good feel for social relationships, way with words, poor analytical
abilities, poor kinesthetic sense, quite poor focus
slow to anger, self-conscious, doesn't often experience strong cravings or
urges, can handle stress, enjoys company of others, assertive, doesn't have
great aesthetic sensitivity, likes to try new things, completely
uninterested in ideas and debates over intellectual issues, not easily moved
to pity, likes working outdoors
Assigned: woodcutting, military, engraving, fishing, bone doctor, lye
making
Note: assign as wrestler to avoid axe problem
bull calf (male, incredibly skinny, gigantic)
Assigned: save for farm
Population 13
This proved too time-consuming, so I switched to just recording their skills, the jobs I assigned them and anything that stood out about them. The list sometimes proves very handy if I need a dwarf for a particular task, but it's still some effort to maintain, so lately I've stopped making notes at all. I now use custom professions to store the most important pieces of information: when the dwarf arrived (for vampire control), what I want the dwarf to do and whether the dwarf is one of those rare gems with few or no blood relatives.
My founders get custom professions indicating what I want them to do, e.g. "Chief Fooddwarf", "Wood Logistics", "M-CMDR" or "CMD". When migrants arrive, I look at each one, assign labors and assign a custom profession. For example, Ducim Athelnakuth w3 weaponsmith FR arrived at Tuloncakoth with the third migrant wave, was assigned to be primarily a weaponsmith (although he likely had alternate duties in the food or masonry sectors) and had few relatives.
Native-born children get no arrival indicator or are marked with their generation (e.g. g2), and after a significant event, I might start a new numbering sequence or assign special names or professions to survivors. If I want dwarves to stand out, they get something in all caps, such as Kadol Relonmeng, r4 VAMPIRE, who arrived with the fourth wave of migrants after goblins reduced Tuloncakoth's population to a crippled miner in the hospital and a bunch of children hiding in the dining hall.
This system isn't the best for finding every thresher in the fortress, but it's not too difficult to identify the important dwarves, and I can look at a dwarf and know immediately what he or she is supposed to be doing.