Just finished reading Alexander Gammie's biography of Morrison, who is rapidly becoming my favorite devotional writer. Morrison was pastor of Wellington Presbyterian Church in Glasgow, Scotland (1902-1928).
Here's Morrison on sermon preparation:
In the morning service, I follow the old Scottish tradition and proceed along the recognized lines of expository preaching. People tell you this old idea must be surrendered to meet the demand of the time, but I feel it would be a tragic thing for the future of preaching if we abandoned this more closely reasoned and intellectually educative method, with its wholesome demand for severe preparation. And I find that our regular congregation, as distinct from the evening audiences, which are of a mixed type, appreciates such solid diet. There are discouragements, of course, such as when a hearer comes to you after a sermon into which you have packed your very best, and tells you that what he enjoyed most of all was the little story in the children's sermonette. But, on the whole, the steady attendance and appreciation of my people at these morning services justify the setting of this high and exacting standard. These sermons involve long and concentrated preparation, especially as I almost invariably handle the greater themes of the Christian revelation at the morning services. This means the treading of well-beaten paths, and therefore makes a heavier demand upon the preacher's thought.
In the evening, my method is, of course, entirely different. There, I allow myself a wider scope, presenting the Christian essentials in a somewhat different setting, and calling to my help every type of illustrative aid that may commend itself to me. I strive to give these addresses a strong human interest, my great aim being to win the attention, in honorable ways, of some, at least, of the vast class of people who sit very loosely to the Church. The touch is, naturally, far lighter than in the morning, but this does not mean lack of preparation. I prepare as carefully for the one as for the other.
Expository sermons in the morning; devotional sermons in the evening. It was the latter which made him famous. They are devotional, but not wispy, ethereal stuff. You can find some examples currently up at my blog.
Morrison did all his sermon preparation, and other writing, in the mornings, where he left strict orders that he was not to be disturbed (except for emergencies, of course). His goal was to have his two Sunday sermons fully prepared by Saturday noon. He would use his Saturday afternoons to relax (mainly by going for long walks; he was an amateur botanist). Saturday evenings were spent in personal preparation for Sunday morning.
He was the first preacher to preach over the radio in Scotland - a 10-minute sermon from Ephesians 6:16, on January 28, 1923.
Before World War I, he preached from fully-written out sermon manuscripts. During and after the war, however, he would prepare detailed outlines and notes, but preach without them. He was not a believer in "mandating" - an old Scottish term which refers to, in the pulpit, repeating a written sermon from memory.
He was a great reader of sermons, his favorite preachers being Spurgeon, Theodore Parker, Canon Liddon, Stopford Brooke, and especially fellow Scotsman John Ker, whom he considered the best preacher the British Isles had ever produced. He was also a fan of Andrew Murray.
Just some tidbits from Gammie's book.