I think you might mean 'O Brother Where Art Thou?' for that comparison with The Odyssey, in which case I think there are similarities of theme. Try to isolate certain themes and then look for examples and quotes from each piece.
For example you could look at the way themes such as isolation, imprisonment, capture, entrapment, escape, challenge and obstacles are presented.
Be mindful also of differences, for example, the number of people attempting the epic journey, what the travellers hope to gain or to find from their voyage and how each character responds to the adventures and hazards along the way.
You can research the whole idea of epic voyages as there are many from Dante's Inferno to the Ilyiad and they are present in the folklore and culture of many cultures worldwide such as the Tain and Beowulf.
Good luck with your comparison