I also had to give flea bathes to Hobbes, my former furry. He was a fairly good size (though not quite as Oliver), too. He would let out a blood curdling yowl just to let the entire neighbours know what a cruel sadistic demon I was and kept it going until we finished, however he stayed there without turning violent, he was an extremely docile boy.
But I am not sure if I can ever gather up the nerve to do 4 of them... wishing you the bestust of luck!