Urethra Penis play

Hi I am new to this site!

I have a question. I like to make my dominate my boyfriend, tie him up, etc. Recently I came across sounding and urethra lube injecting.

My question is can I fill his Urethra with lots of lube with an eye dropper before sounding or will it damage his penis?

Filling his urethra with lube first sounds... different. Just lube the sounding rod. Or is that the point - you want to do something different???

I'm sure you know this but it's worth saying again, just be sure the lube is sterile. The individual packet stuff is best.