I actually do this, but I don't understand why "buying on the way down, selling on the way up" is better than vice versa.
...
Why is this better than doing the other way around though?
If you do it the other way around, "buying on the way up, selling on the way down", you would be buying on the higher price and selling on the lower and be in a loss. Isn't it obvious? When you "buy on the way down, sell on the way up" you actually have a profit at every cycle.