Is there any way to avoid this? What are the best commercial , OR home made remedies, to EASILY remove all that fly crap on my white cars?
Make a little fly outhouse and tape it on the hood with duct tape. 
Keeping it well waxed will at least make cleaning easier.
What do you consider “fly poop”? Is it the orange spots that appear on white vehicles?
Now there is something I had not thought about for a while.
When I lived in Iowa, fly specs on my white car were a common problem. In Sacramento, I have not seen a fly spec for 30 years. The solution, then, is to move West. Failing that, keeping it waxed is your best defense.