I discovered the easy way four decades ago, but foolishly never filed a patent.
If you go to a sporting goods store and purchase a thermal imaging night vision device and in a darkened room put it over the arm every vein will show up because of the differential in temperature. While they are visible, mark them.
Hi
Welcome to the MedHelp forum!
I am not sure why you need to prepare veins for IV unless you are a drug user. There is no way you can do this and it should not be done. Also intravenous medications should be used on you by yourself.
Hope this helps. Please let me know if there is any thing else and do keep me posted. Take care!