Welcome to our forums, but first let's answer one interesting question with another: Did you combine Arran and Kintyre ways using the Claonaig/Lochranza ferry, or was it two separate trips? How did you find the Arran Coastal Way in terms of terrain and navigation

? Our
book is being written this month, so it would be really timely to know

!
Anyway, the Rob Roy Way is linked to the Cateran Trail by a fine cross-country walk from Pitlochry to Kirkmichael, fully documented in pages 55-7 of our
Cateran Trail book. (In truth, the good part begins at Ballinluig, so if you don't fancy 6 miles/10 km of minor road walking, take a short bus/taxi ride Pitlochry/Ballinluig.) So the simple way to combine the two walks is to travel to Glasgow, take the bus to Drymen, walk the RRW to Pitlochry and then use this link to pick up the Cateran Trail clockwise from Kirkmichael and ending up at Blairgowrie. Blairgowrie has no rail service, but Perth has (only 15 miles away), or buses go direct to Edinburgh (a further 45 miles).
Of course you could do the whole thing in reverse (Cateran Trail before Rob Roy Way), but proceeding north-easterly makes more sense in Scotland (prevailing winds, progressively more rugged scenery, therefore it's the way the directions are written).
One tip re Cateran Trail: two years after the book came out, we produced a free upgrade card for the route section Dalnaglar to Kirkton of Glenisla which changed drastically and for the better: make sure you get this if/when you buy the book, not all distributors/shops are careful enough about checking it hasn't fallen out

Hope this helps, let us know how it goes pls.