A 99 euro vacuum food saver will get you a long way in sending drugs worldwide. Combine that with some clever packaging and the chances of it getting caught at customs are pretty small.
Heard the same from friends - they were sending meat products that were a little on the grey side of import rules across a border. Vacuum packing + bleaching it overnight seems to keep the sniffer dogs away. Whether that works for drugs I can't say though.
Dealers use moisture barrier bags that are heat sealed now as apparently dogs can detect vacuum sealed bags though unclear if it's outside contamination, like somebody putting together a package in a room full of weed shavings or smoke.
Both heat sealed and vacuum sealed are air-tight, so that difference should be a non-issue. Its the stuff sticking to the outside of the bag that might be an issue. For meat I'd imagine bleach should do the trick...no idea what you'd need to remove drug traces though. Not a skillset I plan on deploying anytime soon so didn't research it.