The best way to do this is with the supply truck, it has 2 supply crates, both of which are worth 150 supplies for a total of 300. The Support class can also drop 50 what seems like every few minutes. Supply trucks are spawned in by a Commander and can be resupplied back at your HQ by driving near a loading crane.
My recommendation is to just play the game, instead of dumping it randomly and resupplying. You're going to be playing for quite a while if you plan to 100% and will easily surpass the amount needed for the achievement. You'll also need to level up the Support class to level 8 as it is, and the best way to do that is to delivery supplies and help build structures.
If want you can find an empty server and spawn as commander, this way you can dump all the supplies you'd like. But as a said I recommend you just play normally.