My good grey jumper has had two holes in the elbow since last winter. This week I borrowed a book on darning from the library and tried (sample entry).
The first darn pulled the wool into a pucker. The second, done over a wooden spoon to keep it flat, is lumpy but holds. The book says the third one is always better.
If you know a good way to keep the tension even, write to me. I will add the best answer to the end of this entry.