Here's one at work in Argentina:
http://miguiaargentina.com.ar/Imagenes/b/783264994-2-letrist...
from this page:
http://miguiaargentina.com.ar/empresas/letrista-coria-cartel...

https://en.wikipedia.org/wiki/Signwriter

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Note added at 8 mins (2017-02-15 21:51:54 GMT)
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"Traditional signwriting is enjoying a revival largely due to North American writers and their growing influence on English and European sign artisans such as David A. Smith in Torquay, England. Traditional signwriters use methods closely related to those of their forebears in this craft and do not depend on technology - they are able to set out a sign with chalk and write it by eye in freehand. They do not rely on fonts and normally have their own individual lettering styles, yet also have the ability to render fonts closely to brand, as in architectural design briefs, for example."
From the Wikipedia page just cited.

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Note added at 14 mins (2017-02-15 21:57:59 GMT)
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This page, written by someone in Rosario whose father is this kind of "letrista", is quite good fun:

"Bien, mi viejo como Letrista se dedica a pintar y decorar salones de fiesta, inflables, negocios, casas, etc. La verdad que se la rebusca bastante bien. Quisiera aclarar para que no se confundan que esto NO es rotulación, mi viejo hace todo a mano, a pulso y fundamentalmente con pintura, no es el caso de la rotulación que son letras impresas plegables."
https://www.taringa.net/post/offtopic/18907936/Mi-papa-es-Le...