Heres a simple method of rating a price of your own.

Jot down the win percentage of the
5 pre-post Favs from a Good track condition performances only. (I have found this a good way of comparing apples with apples.)

In other words ignor it`s past performance over Fast, Dead, Slow & Heavy tracks only target it`s wins on a good track.

Once you have the percentages ,convert to a price.
This is how I do it.
E.G. 50% win on good track conditions only, would be 100 divided by 50=2/1 chance or $3.00.
40%=2.5/1=$3.50
30%=3.30/1=$4.30
25%=4/1=$5.00
20%=5/1=$6.00
10%=10/1=$11.00

You will notice I have rated the percentage outcome 1 point higher than expectation to its past history, if history were to repeat itself.
We are trying to instill some value here.

Bet all these Mules if price is same or longer than your accessed market.

Try this out on Fields of 8-12 runners only,where the whole field has had 2 starts+
Otherwise no bet that race.

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Cheers.