I usually have all my melee troopers at training 24/7 in 2 to 4 dwarf squads. If I have time, I wait with the draft until the designated recruit becomes legendary miner or pump operator (with screw pump gym) to increase their attributes. They'll be pretty ripped anyway if they live to be Legendary in military skills, but early on it might be important for them to have the extra speed from strenght, or the endurance/toughness not to pass out in combat. Until they are reasonably skilled and equipped, they don't fight enemy soldiers, but I mass-pit everything I catch and disarm in the room they train in. Even later, their primary purpose is to clean out enemies clogging the trapped entrances, so aside from the occasional unharmed and pissed off, but outnumbered goblin Master [insert weapon name here], their job is to finish off unconcious enemy wounded. Late game (5-10 years), when they grow up to be Legendary in weapon skill, Fighter, Dodger, Shield User and Armor User, they cut through goblin infantry like a hot knife through butter, provided they have at least steel armor and weapons (silver for blunts, copper for shields), which by Iron goblinite plus local/imported flux they normally have at that point. Forgotten Beasts of course are still very very deadly for them, and even goblins can get lucky.
As for ranged support, I just make as many crossbows and quivers as my population cap, and a lots of bone/cheap metal bolts, and I draft everyone who isn't a miner, woodcutter or melee soldier into 10-dwarf squads with a uniform of crossbow, shield, metal mail shirt, metal breastplate, metal headwear, metal legwear, metal footwearx2, metal handwear. Equipment priority is lower than melee squads, so they only get the leftovers. They have a good chance to outright kill snatchers and thieves as soon as they detect them, and if several of them are nearby, whole ambushes can be crippled by pain, and given good enough equipment they have a good chance to survive melee until reinforcements arrive. And by reinforcements I mean the rest of the fortress unleashing a hail of *cat bone bolt*s and the soldiers rushing in to kill the vomiting, fainting greenskins, who by that point are probably lacking either weapon or shield.