No, you can't get by with just your smart phone and the Navionics app, you definitely need the Clyde Cruising Club Sailing Directions too. They go back to the first edition in 1923. These directions are regularly updated, and are spiral bound which makes them robust and very handy. The ones relevant to this area are: 'Kintyre to Ardnamurchan' (2020) and 'Ardnamurchan to Cape Wrath' (2017). You can download the amendments from the Clyde Cruising Club website.
Some may wonder why these sailing directions don't already contain the sort of information this website provides, or indeed that can be found in some of the glossy books describing the anchorages around the English coast. In my no doubt biased view, this is all for the best. To enter the anchorages you need a water-resistant easy-to-fold-out book wedged under a winch handle in the cockpit telling you succinctly how to get there safely. You do not want it cluttered up with the sort of stuff I have on this website — which comes in useful only when you are safely anchored, kettle on the boil or drink in hand, thinking about going ashore.
The earliest first 'sailing directions' must surely be those published by Murdoch Mackenzie in 1776. He was an Orcadian cartographer and hydrographer, and the first to produce recognisable charts of the seas around the British Isles while working for the Admiralty. You can find the book on line, and also many of his charts at the National Library of Scotland. Mind you, some of his metrics for distance would strike one as quaint. For example, the rock in Canna Harbour, now incorporated into the pier, he described as being "about a pistol shot from the shore".
Then, in 1896, came Part 5 — the west Coasts of Scotland, the Orkneys, and the west coast of the North Sea — of Frank Cowper's detailed Sailing Tours: the yachtsman's guide to the cruising waters of the English and adjacent coasts. There is more here than just sailing directions, but little information about what there was ashore, and he did not describe many human interactions. But his descriptions of sailing with no engine in strong tidal streams are pretty hair raising, particularly bearing in mind he was often single-handed. A lot of the pilotage information could be used today. His obituarist in Yachting Monthly wrote in 1930: "From his earliest days Mr. Cowper took cruising to heart and probably did more to popularise this particular way of life than any man of his day. It is almost inconceivable to us now the prejudice which then existed in the public mind against the man who did not employ hands aboard his yacht. But it was through this veteran singlehanded sailor's adventures and writings that the public began to recognise small yacht cruising as a sane man's pastime".
‘Welcome Anchorages’ and the ‘Sail Scotland’ official guide are not sailing directions as such, but both are free and useful guides, updated every year, and you can pick them up in chandleries and marinas, or download them.