A new publication, of roughly 150 pages, has come out under the auspices of the Schola Cantorum, written by Augusta Campagne and Elam Rotem. It is available for free.
The Preface states: "How to accompany on keyboard and plucked string instruments in the period around 1600, when basso continuo notation started appearing, has long been a subject of interest to scholars and musicians alike. Research has mainly been based on the few theoretical treatises available, which, though informative in some ways, tend to be rather vague and unclear in many others. Intabulations are also regularly cited as sources for the practice of concertare (playing in a consort of voices and/or instruments), but until recently only in passing, and thorough studies have been lacking. Practical advice on early basso continuo and on how to play upon the bass has been scarce. In recent years various studies as well as new sources have appeared, which have approached intabulations and scores from a different perspective. This has led to a more concrete and practical knowledge of what was considered standard playing practice when accompanying around 1600.
The aim of this project is to bring together the knowledge accumulated in these different studies, adding some new material and insights. This evidence is then used to reinterpret the well-known treatises and present the most current knowledge about accompanying upon a bass."