I always keep the same routine with bath time, we comb out first, and then give a treat, then bath, treat again, then comb out/dry, and treat
They get used to this and know what to expect. Also in the beginning I took my time with them, made it a good experience.
You can put a washcloth in the bottom of the bath/sink so that they don't slip around, and that makes them more secure. They also do better if the water isn't rising up around them, mine really hate it if I plug the sink. Now they get jealous if the other is getting a bath or brushed out, they really like it and the extra attention.