So, from this I gather that Dwarves will use the Cirth when writing in Khuzdul, but that most will probably also know the Tengwar and use it when writing in languages where it is others' script of choice. I gather that Elves will generally prefer the Tengwar, but that almost all of them will also be familiar with the Cirth.J.R.R. Tolkien, in Appendix E to the LotR trilogy, wrote:The alphabets were of two main, and in origin independent, kinds: the Tengwar or Tîw, here translated as ‘letters’; and the Certar or Cirth, translated as ‘runes’. The Tengwar were devised for writing with brush or pen, and the squared forms of inscriptions were in their case derivative from the written forms. The Certar were devised and mostly used only for scratched or incised inscriptions.
The Tengwar were the more ancient; for they had been developed by the Noldor, the kindred of the Eldar most skilled in such matters, long before their exile. The oldest Eldarin letters, the Tengwar of Rúmil, were not used in Middle-earth. The later letters, the Tengwar of Fëanor, were largely a new invention, though they owed something to the letters of Rúmil. They were brought to Middle-earth by the exiled Noldor, and so became known to the Edain and Númenóreans. In the Third Age [the Tengwar's] use had spread over much the same area as that in which the Common Speech was known.
The Cirth were devised first in Beleriand by the Sindar, and were long used only for inscribing names and brief memorials upon wood or stone. To that origin they owe their angular shapes, very similar to the runes of our times, though they differed from these in details and were wholly different in arrangement. The Cirth in their older and simpler form spread eastward in the Second Age, and became known to many peoples, to Men and Dwarves, and even to Orcs, all of whom altered them to suit their purposes and according to their skill or lack of it. One such simple form [of the Cirth] was still used by the Men of Dale, and a similar one by the Rohirrim.
But in Beleriand, before the end of the First Age, the Cirth, partly under the influence of the Tengwar of the Noldor, were rearranged and further developed. Their richest and most ordered form was known as the Alphabet of Daeron, since in Elvish tradition it was said to have been devised by Daeron, the minstrel and loremaster of King Thingol of Doriath. Among the Eldar the Alphabet of Daeron did not develop true cursive forms, since for writing the Elves adopted the Fëanorian letters. The Elves of the West indeed for the most part gave up the use of runes altogether. In the country of Eregion, however, the Alphabet of Daeron was maintained in use and passed thence to Moria, where it became the alphabet most favoured by the Dwarves. It remained ever after in use among them and passed with them to the North. Hence in later times it was often called Angerthas Moria or the Long Rune-rows of Moria. As with their speech the Dwarves made use of such scripts as were current and many wrote the Fëanorian letters skilfully; but for their own tongue they adhered to the Cirth, and developed written pen-forms from them.
I'm not so sure about the Men of Dale, though. Do they use the Cirth for Dalish and the Tengwar for Westron? The cirth when carving and the Tengwar when writing with ink and paper? How common might it be for Men to know one but not the other?
Among those Men who do know only one script, will the Cirith be more common among the Men of Dale, but the Tengwar more common in other Mannish lands (Gondor, for example)?