Not a fan of this technique as I believe it encourages too much tension on the chain.
If you ride a bike with a singlespeed drivetrain you really should learn to tension the chain properly, it's one of the few skills you need to keep your bike running good, it's a lot easier to master than say indexing gears and it's arguably more related to your safety than the likes of gear indexing, especially if you ride without a (rear) brake.
I would encourage you to use your hand between the tyre and seatube to set the tension initially and to then 'walk'* the wheel backwards or forwards to fine tune the tension.
- loosen the nut on one side and use your free hand to manipulate the wheel side to side at the point where it passes the chainstays. Repeat with other side nut if neccesary. Moving the wheel towards the drive side chainstays will increase tension, towards non drive side will reduce it.
To be brutally honest though, if chain tensioning is beyond you I'd suggest you see if there's a mechanic or just a more mechanically able mate that can be persuaded (beer, Jaffa cakes, etc) to give you some advice/lessons.