I prefer the Dutch betting and the method I use is as follows.
5 runners is the absolute max and I prefer 4,3 or 2. If you can't get the race to 5 or less then leave the race alone.
Win betting only.
Back your main selection to win the most eg 5 times more than the others and then the others bets are covering bets that I like to get a 20/25% profit on turnover for the race on.
Its hard to do sometimes if all your selections are short in the market.
I tried to add a large place bet in as a cover once on the main selection (this was to cover no winners and the main selection running 2nd or 3rd) but 2/3 losses in a row had the bank struggling.
Thats the way I try to work it but then I still go out to work each week.
Good Luck from one Gym to another JIm