Lots of the major chains do a plug patch combo for free, or around the 20 dollar mark.
The metal is used as a guide to go through the hole and is then pulled off leaving a plug and a patch, its what most shops use, works well.
This is a normal patch, no plug
They both work great if put on properly.
remove nail or whatever
dismount tire, ream puncture until it is a little smaller than the plug
buff inside of tire around puncture smooth
apply cement and allow it to become tacky
run metal guide through puncture
pull through other side of tire, when pulling through the metal sleeve should come off plug should now be sticking out of outside of tire and may need to be pulled on to pull the patch on the inside flat.
run the plug stitcher over the patch in many different directions
This should make the clear plastic on the back of the patch pull up from tire
Run stitcher over patch again to make sure all the edges are stuck to tire and sealed.
remount and rebalance
If you dont know what you are doing its easy to damage a tire, by buffing through the rubber on the inside and into the cords or damaging the carcass when reaming.
Just have someone do it, it will save you lots of time and you may end up finding someone to do it for free, those tire guys do them all day everyday they are gonna be way better and less likely to damage something.