When an individual has no order for a month, or is involved in a months order where you set a min order(3 out of 4) selected, and he is 4, that dwarf will individually train(weapon train) at a barracks, if he has no job. There is a waiting period where he will wait for a job, once its up, will go individual train. The waiting period on the Active schedule is much less than on the Inactive schedule. So if you turn off that dwarves hauling labor, and other labors, will weapon train more.
I will give future draftee peasants pump op labor, just until they become novice in it, then turn off the pumps, and draft them.
If you have the time(hiding behind the gates in terror), set up a basic training squad. This is the only time I will use danger rooms. Have a dwarf with basic military and a decent teacher skills, assign them to a danger room, armored up. First season is to train armor user skill. At this stage do not have them equipped with either a sword or weapon. The armor user skill does not seem to help with defense, but does give the trooper good speed. Lowers encumbrance from armor. Next season equip with a shield, to train up shield skill. Then next season, drop the shield, add the weapon you want them to use. When they are in the danger room, will parry with their weapon, which will increase weapon skill. Last season of the year, reequip with a shield, let them keep the weapon. For all the months that year, will also be receiving lessons from the militia commander. Which he will also be getting danger room experiance, and teacher skills. By the end of the year, the soldiers should have decent military skills, so you either start a new squad with the trainees, or several, and assign them a barracks beside the danger room. Now draft some new soldiers for the basic training squad, and repeat above.