I think a lot of guys just put their shit in their checked in baggage and dont even think about it lol
Depends on the country, non western countries i dont think customs care much.
I have had my luggage scanned in singapore several times they only look for obvious stuff like weapons or tons of pills or organic matter (food)
To be safe i never carry any oil or vial or seringes anywhere. usually a few adex tabs
If you look like a bodybuilder and travel in western countries you have a big chance to get searched
Countries like australia or new zealand are very strict, i wouldnt take any chance in the us too. hide yamagishi actually got busted at LAX from japan basicly carrying all his prep stuff on him. he spend time in jail if i recall correctly