I've not done the actual walk, but I do live in Ayrshire and some of the scenery can be pretty impressive. As mentioned, the views over to Arran, Bute etc are lovely.....stunning if the weather is just right.
Accommodation shouldn't be a problem either, plenty of B&Bs dotted around ayrshire. Ayr, Girvan, Saltcoats & Largs would possibly provide more B&B options.
I'd probably do a section at the Southern end, then a section that takes in Culzean; there are some nice walks in the grounds of the castle which is also worth a few hours of your time (links with Eisenhower and the US that may...or may not be of interest) and then one to the Northern end from around Saltcoats up past Largs and Skelmorlie. I reckon that would give you 2 or 3 days walking and would provide enough variety in the coastal views to avoid being boring.
Decent rail links at Stranraer, Girvan, Maybole, Ayr, Kilwinning, Stevenston, Saltcoats, Ardrossan and Largs (the line ends here) would be the stations you would possibly be looking at utilising if that's of any help to you in your planning.
Midges aren't too bad around the coast either (more chance of a breeze to keep them at bay).