i feel your pain about the overwhelming information you think you need to collate to draw up a fluke plan for your property. hopefully you have helpful vets (i dont) I even sent poo samples to the moredun foundation who do free fluke tests as they are a research institute for the disease. They found nothing: BUT that does not mean you do not have a fluke problem! FEC for fluke are pointless, you will likely get a negative egg count (esp this time of year) but it still be adult fluke burrowing through the liver causing problems.
My sheep have grazed this property for 10 years. There was anecdotal evidence of fluke (ie sheep from here having condemned livers at slaughter) but it is not something farmers here treat locally- it is very site specific.
I bought ducks last year: ive still had sheep go down with symptoms of fluke so dont think they are the answer. i began a programme of treatments for my guys to avoid them getting sick before i treat (cos if they have symptoms then their livers are being compromised) but i still get sick sheep: ususally they present as having belly ache, but one ewe has had the very obvious bottle jaw, twice now. They respind to treatement within 48 hours. Thats how i know it was fluke and not something else. Trichlobendazole kills nearly all life stages of the fluke but there is a risk of resistance with over use so only use it if an animal is sick. If you are treating preventatively try to use a drug that targets the life stage most likely to be present- eg closental early in the seasonl, then albendazole.
Also non of my sheep have scours from fluke. And it is recommended not to use a combined fluke and wormer product: Lambs have more fragile liver than adults so probably are affected more, but note adults do not develop resisitance to fluke (they do to worms to a degree)
*hint to get poo samples from pet sheep: leave them to lie down. Whe you go in and disturb them the first thing they tend to do is get up, poo and wee!