If you follow it from Ravenglass you have a nice easy Coastal path all the way to Carlisle and you can use the railway to to get to the start of any section. It meanders for no good reason, other than to make up distance between Carlisle and Lanercost and on this bit you are better following the minor roads on the map. Otherwise it is a good route with plenty of alternatives, nice climb out of Greenhead and the Military road is not as bad as it looks but there are alternatives, other than dropping down to the Tyne valley. I would use the train rather than the bus, better services and if you have a railcard not much dearer. Newcastle is not too bad all the way to Wallsend but you are not allowed to take bikes on the Metro, so you have to go on to North Shields and cross the Tyne via the ferry and either ride to Sunderland or follow the Tyne back to Newcastle. I belive part of the Tyne tunnel is open for cyclists but I have never used it yet.