When I work at a place where I start my own IVs, even for sort procedures, I use lidocaine and stick in at least an 18, and often a 16 in the wrist or forearm. They usually get taken out by the end of the day when the patient gets sent home. With a high flow rate on the fluids, patients seldom complain about the propofol burning.
When I work at a place where the nursing staff starts the IVs, I often have to contend with 20s and sometimes 22s. Since you can not run them very fast and they are often in the hand, the propofol burns unless I use a dose of lidocaine first.
There is a lot to be said about starting your own IVs.