As I understand the posts. I think I approach this as Bill V. and Alydar_David, (but the ultimate answer lies in your own records).
I also don't care, until betting time, what the odds are. For me it's about hoss selection, and the wagering decision is separate. I do lots of races, so I also pass lots of races, when it's time to bet. Many times you can get a feel , just by looking at the horse, what the public is going to do with it, and also look at the morning line.
(I often think I should set up a study/system of "favorite validation" ... but that's for later).
When the 2, (and VERY rarely 3) horses are chosen for the dutch, .......(you may find instead of flat betting, you may want to look at calculating a proportional dutched entry, and bet it that way, although you will have to spend more than $2.00 on the entry, maybe $2/3, or $2/$4 or whatever)....then I calculate the dutch "payoff" to decide if the bet is greater than my minimum payoff number, (which you should calculate from a minimum break-even formula). If you win about 50% of your races, and for example play 20 races per week, your break-even payoff would be about 1.06, (both horses would have to average out slightly more than 3/1).... and THAT's only break-even.
There are dutching instructions and calculators, charts, and break even formulas in Follow Up #2 and 3. There are also dutching calculators posted on the web.I sometimes use the one at :
http://www.bettinggenius.com/betting...ng-calculator/
I will post my own when I get the spreadsheets ready.
(I'm working on posting speadsheats with all the formulas, but it's going to take me a while to get mine cleaned up...they are a mess).
That's how I do it.