To be 100% honest with you, you're not in any shape or form ready to start painting trains. You're going to have alot of writers not even acknowledging your work and quite a few or going to be bummed you even painted the train especially depending on the kind of car. Read the sticky threads on here first, titled yard safety and keeping spots chill. You need to practice a hell of alot more. Trains are not little chill spots where you can just go and do whatever. If you want to make a name for your self and be respected as a writer, now is not the time for you to just go and hop on a freight because it seems like its the next cool thing.
Even after years of bombing and painting walls, my first 10 freights I done I highly regret and hope the have been gone over already. You will know when and feel comfortable to do freights when the time comes. Your style and can control are not on that level yet. And if you go and ask this crew leader you speak of to go to the yard he is going to tell you something similar to what Im telling you and bottom line the answer is No, do not go and try to paint freights.
And when the time comes that your pieces are looking dope and you want to do your first freight have a writer bring you, show you the ropes, and best ways in and out of the spot without being seen.
Best of luck to ya, and just practice, practice, practice judging by your work you might be ready to do a freight in another 2 years. Dont take offense Im just being real with ya.