I've been teaching my 2 year 8 month old son to take a small piece of toilet paper and dry his penis then get another larger piece of toilet paper to clean his butt when he pees and poos in the toilet. I learned a couple months after he started using the big potty that my wife has been having him use the same piece of toilet paper in both areas cleaning his penis first then his butt - as thats what girls do, wipe front to back with the same piece of toilet paper. To me, I would think boys and girls would just do it differently besides boys can't wipe from front to back in one motion anyways. What is the best way for boys to clean their pee and poo after using the toilet?
Not sure there is a 'proper' or 'best' way. Both the ones you describe will work.
For little children the most important thing can be to make it easy for them to get it right so I'd suggest letting him use whichever method he prefers could be the best option.
In any case, you should let him know that both ways are right.