The Essex Way, which runs between Epping and Harwich, is described in a PDF file, The Essex Way, from Essex County Council. This contains an annotated sketch map, and the telephone number for local public transport enquiries. Note that the essexway.org.uk site refers to a race along the route rather than to the route itself.
Peter Aylmer’s Walking in Essex (introduced in, and linked from, an online article) gives more detailed public transport information, including links to operators’ and aggregators’ websites, as well as pointers to other facilities such as pubs and cafés.
Green Walks UK has compiled a public transport distance matrix for the route.
There is a book of circular walks to accomplish the whole route (but one may linearise it by ignoring the turnback sections!).
Lwalks.London 