You just press it one time and it goes down. You don't just hold it there.
Do you know how these things work? An erection is a steady supply of blood moving through your snake. What you've described is forcefully shutting off that blood flow, but pretty far down the line as-well, I wouldn't be surprised if you were cutting off life blood to a few other sensitive areas.
I'd also rather have a boner and shift it down the pant leg rather than finger my gooch in public.