We now only offer priority mail because of the unrestricted amount of shipping supply we can use to protect the paints! Because of recent damages with our packages via first class (even with a lot of bubble wraps), They were arriving with damages so we are going fully with priority mail. We do not have months of fulfillment time like other do, priority mail will be worth your money.
As far as the paint goes, any paints that are $6.99 requires a bit more precision when spraying. They can't be sprayed wet from the first coat so something I would recommend you do is spraying light coats always on primer and be very patient with them. Usually, 4-5 passes should be able to cover the body fairly well. but once you have 2-3 coats down, you can apply a bit heavier by slowing your hand down rather than adjusting the needle.
I hope this helped!