Bathing wont sort the problem as the eggs stick much like nits do
You need to seperate the hair and apply the spot on to the skin to make it work. Which it does or all people with LH cats would have a huge problem and big blood loss
Have you got an assistant for the feisty ones? If you fold a towel and wet it and lay this in the bath they wont feel so dodgy, its something for them to hang onto.
I wouldnt get in the bath as cat climing up leg would not be nice
Some dont like a shower head so a cup poured over them may suit better.
Trial and error, good luck