I feel you have the right approach with only targeting 1 selection per venue.
There is a lot less chance of getting bit.

Here is a selection plan that works well.

5.50 PLAN.
.Pull up a pre-post newspaper market from any newspaper or an online
pre-post market like racingandsports.

Different newspapers may have different price, that's OK.
They may be different selections , but they all end up with the same result long term

Go through each race & stop at the first selection we come to, where its price is 5.50 exactly.

.No bet, if our selection ends up being the live market Fav.

If a draw , take the one with the smallest TAB number .
e.g. Take 2 over 4

Do this for each venue.
One per venue.
If we get bit , keep going with the other venues.
We will recover along the way.

Sometimes there wont be a selection for that venue, that's OK. just don't try & force a bet that does not qualify under the rules.

Bet 1% of bank.
Max price 9.00
Must not be Live Market Fav.

Cheers.

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Cheers.