One thing that nobody seems to have mentioned, but should be obvious from the various militarily savy posters comments, is that mixed weapon squads train slower than single weapon-type squads. From all I have seen, having a squad of four with four different weapons is only marginally better than having four individual squads of one dwarf each as far as training time goes. If you set up squads to train a specific weapon, they will train much faster because the Udib the axe dwarf recruit won't be trying to learn spear or sword skills from Datan or Bem, or hammer skills from Rigoth, he (and everyone else in the axe squad) will be learning axe skills from whoever has the highest skill in axes in the squad.
Have a trainer (teacher) for each weapon type you plan to use. Keep the "class" size small while the teacher skill sucks, and grow the class size as their teacher skill improves.
Myself, I normally use squads of 4 to train in the beginning, then split them up to be the captains of four squads of 4+ once they've had 18 to 24 months of training. Thats usually Skilled or better, with zero teacher/student skills at start. In my current fortress I'm using 2 dwarves to start with due to not having any stone for most of the first year, and only having 21 dwarves after the third migrant wave (two of those children).
And for those that tried to tell me before, you were right, two dwarves do train up faster than four. Not by much, perhaps 50% faster, but it is noticeable.
My long term goal is to double my military size every time a full "class" of recruits reaches Competent in their assigned weapon. Start with four, split them up when they get to Competent (or more likely Skilled, with teh slow rate my fortresses grow
). Then when their squads of three to four dwarves reach competent double it again, or just double the number of dwarves in each squad. Once I have my initial squads up to Competent or better, I would create a training squad, and put my best Teacher as its captain and have hir crank out Competent recruits.
Four random migrants with 12 months of training as speardwarves, in leather armor and using copper spears completely trounced an elven archer ambush one time. I admit, they closed to melee range unopposed because the elves were busy
torturing targetting a cat, but after killing 10 of the 16, and stabbing the war lion in the back of the head to kill it on the second hit (the first hit made its tail bleed), all without taking any damage at all, means work arounds for training aren't needed.
In my opinion, stating you need to use work arounds to train soldiers in 32.18+ is like stating its annoying that your crafts dwarves have to walk all the way down to the mines themselves to get stone to make mugs, but you can work around that my setting up dedicated haulers and/or add a stone stockpile near the craftsdwarf workshop. It isn't a work around, just a bit more efficiency at the cost of a little more time in setup.