This feels a bit like recommending a cheat for a computer game and thereby taking the enjoyment out of it but if you get to around page 500 of Ulysses and you are really struggling with the hallucination sequences then it helps to know that if you are using a book without footnotes then there is a way of quickly getting back in touch with the direction the narrative should be going in.
This comes with a caution - only use if desperate because it can spoil the reading experience – but there is a cheat’s guide to Ulysses on the BBC.