Here is another Lay method.
Target preferred runner, priced 4.50-5.50

Bet goes...
6 lots of...
1 1 1 1 1 1
2 2 2 2 2 2 ect
3 --------
4 --------
5 --------
6 --------
7 --------
ect.
Win, lose or draw until all losses recovered then start again.

You will see that only a few win in this price range.
Often with long strings of outs.

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Cheers.