Easy Peasy, Lemon Squeezy. Just go to export_descr_unit.txt in the Data file. Say you want to make British Peasants train in 0 turns:


Code:
type             barb peasant briton
dictionary       barb_peasant_briton      ; Barbarian Peasants
category         infantry
class            light
voice_type       Light_1
soldier          barb_peasant, 60, 0, 0.7
attributes       sea_faring, hide_improved_forest
formation        1.2, 1.8, 2.4, 2.4, 6, horde
stat_health      1, 0
stat_pri         1, 0, no, 0, 0, melee, simple, piercing, knife, 25 ,1
stat_pri_attr    no
stat_sec         0, 0, no, 0, 0, no, no, no, none, 25 ,1
stat_sec_attr    no
stat_pri_armour  3, 1, 0, leather
stat_sec_armour  0, 0, flesh
stat_heat        2
stat_ground      2, -2, 3, 2
stat_mental      0, low, untrained
stat_charge_dist 30
stat_fire_delay  0
stat_food        60, 300
stat_cost        1, 150, 100, 20, 30, 150
ownership        britons
Where it says stat cost, just change the 1 that i have highlighted into a 0. Do this for all units.