Counter to the experiences expressed above, I found marriage arranging relatively quick, though complicated.
First, a little backstory: I unknowingly embarked from an entirely extinct civilization. Once I realized that no more migrants would be arriving (ever!), I started looking at ways to sustain my fortress long-term. Unfortunately my two hard-coded migrant waves had only delivered one married couple. While they reliably pumped out kids, there would be no dwarves for those children to marry.
I tried creating a single, small meeting area and suspending most fortress operations. After years of leisure most of my dwarves had formed many friendships, but only one couple had entered a romantic relationship. Clearly it was time for a more direct approach.
I examined my dwarves using Therapist to identify age ranges; a full third of my population were "old maids" (old women with no prospect for a mate). Of the remaining dwarves, I examined their "orientation" in dfhack to exclude the three who weren't interested in marriage. That left the one romantic couple and two other potential couples. I attempted to match traits, but with such a short list it wasn't possible (nor, apparently, was it necessary).
I created "pre-honeymoon suites"; specially modified bedrooms for my chosen dwarves:
Of note, the rooms contain two beds (each defining a bedroom), enough fancy furniture to make the rooms high-quality, and impassible furniture (statues) to prevent the owners from avoiding each other. (Designate the rooms *before* adding the statues, since you can't designate a room through them.)
I then assigned the bedrooms appropriately to my chosen dwarves, and removed all meeting areas. I specifically did not lock the dwarves in, so they were free to leave (to eat, drink, and work, though I did reduce their work schedules significantly). This detail might be key since it keeps the dwarves happy (good dining facilities, decorations, etc.) while allowing them to enter each other's presence repeatedly. Returning dwarves would often stop in the doorway, presumably to "talk" with their arranged partner (if they never left sight of each other the talking might occur much less frequently).
Results: All three couples married in three months. (The "romantic" couple was actually last, presumably because the planter consistently kept harvesting plants until I specifically forbade it.)