Hi Yacorob1,
Being something of a Racing enthusiast, I have experimented with some Dutching systems in the past.
Personally, I would never try to create a "workable system" from racing with the intent of making an income from it, because the bookmaker's edge is already built into any odds you take, so you''re already up against it to overcome that and show a profit in the long-term.
The most workable method I found for Dutching was to wait for races where their are a small number of runners, all with odds against (ie - nothing odds-on). That way, you can cover the main 2 or 3 runners in the market that have the (supposedly) best chance of winning.
I must stress that Racing is simply an entertaining hobby for me, and I would never try to make betting into a serious business opportunity!
Good Luck!
Thanks
Damian