I use coat hanger, welding rod, or whatever I can find in the shop and usually have larger holes in the tang than the rod because I am not great at making knives so the larger hole makes fit and finish easier for me. Perfect holes through and through require perfect mock-up and although I am sure I could get it I don't want to take the time or deal with the frustration.
Modern epoxies will hold forever even without pins so most pins are really for show.
I say that last statement tongue in cheek as I am not selling my knives. Those that are I imagine will feel differently about pins and epoxy so take it with a grain of salt. I am just trying to say that if your pin holes are not perfect and you use a quality 2 part epoxy you will be happy with the strength of the handing.