My Friend and I did it a couple of years ago, just the two of us. As previous poster we took the scenic route and tried to catch some coastline too. think we averaged just over 100k a day. We went from Malin to Mizen and stayed in Schull for a couple of nights afterwards.
Malin to Donegal town;
Donegal to Enniscrone
Ennicrone to Louisburgh
Louisburgh to Galway
Galway to Lahinch
Lahinch to Killarney
Killarney to Mizen
We found some guy that runs a business of carrying baggage for hill-walkers etc. He collected our stuff from B&B each morning and it was waiting for us when we got to the next one.
Great week, we still talk about it. We did it in August, 1 rain shower 0 punctures
Seems a great route btw, I personally couldnt be doing that without getting some scenary in, going up thru the midlands would be grim imho.