Hm.. seriously - pressure is not intended . flushing with a lot of water indeed. The problem no matter what - is, if there are fragments of bones, projectile .. etc that could be pushed in the meat.. - What I do is I rather flush with low pressure - and more volume. ( If its a boar that has just bathed in mud ..
So what I do - if its female anything mammal / nipples and underlying material is cut away, - ( male respectively -- see that nothing outer skin comes into contact with open carcass.
Most important channel of bullet and anything of digestive system is out and all channels and natural body openings or were they were when dressing completed need to be flushed. - this will also reduce temperature pretty fast and is easier to transport to cooling unit.. where the carcass will hand at somewhat 3-7 centigrade..
So ususally I need for first flush at least 15-20l water. at home / respective my butcher who is doing the rest of the job there is a much larger hose and there the rest of the skin and so will be flushed again entirely / also outside if it is a boar. - What I think of is either mount a larger water canister on the ladder.. a litte pump and hose. / Perhaps roof rack water tank of 40l.. at the moment I carry a 20l canister with water separately and 10l for cleaning of hands, knifes and a sanitary sterilising liquid for
knifes (I use a set of F Dick's.. )
and
this one.. by Löwe, serving me now sind last 10 years w/o issues.. all always easy to clean and to be resharpened..