Dogs @ mail customs are not trained to sniff out steroids, just drugs, animals and plants/vegetables. the glass enclosure even though it helps is not foul proof. if that were the case, you'd see all the cocaine smuggled into US in glass containers...
Amps and small vials just put them inside a cassete box, tape them to they don't bounce around and ship them in small envelope, with bogus return address.
bigger vials ship them in invididual padded envelopes, you'll have nothing to worry about.