i am going to install a nitrous system on my camaro and do alot of racing with it. so i bought some nitrous in a big tank to fill my own bottles at home. I know you have to pull a vaccum in the tank to be filled and dont know how much vaccum to pull? I have "heard that i am supposed to freeze the bottle before filling it?" for what i dont know? I dont know how cold am i supposed to get it. I know that i have to use a charging scale to measure the weight of the bottle as I fill it, to get the proper weight. Any info would be appreciated!!! Thank You!!!