Unit Quality Upgrades Slowly

It seems like my unit quality upgrades slowly. i set a target of 450 weapon and ammo quality but it'll take forever to get there. What determines upgrade speed? Would more supply units help? I have lots of AQU and WQUs available

On auto, each month your weapon and ammo quality are upgraded 2 points. You are correct that there is some amount of degradation in weapon and ammo quality, similar to what corps experience with losing some of their upgrades over time. More upgrade products do not effect this, unless you simply have an insufficient number of them. Supply units have no role in assisting with upgrades though their quality will average with delivered weapons and ammo to their target.