Greetings Elisa, and welcome. Like you, I have family lines in both Coahuila and the NR areas, specifically Aguascalientes. Let me know if you want help with the brick walls. I recently got past a few in Coahuila and Agc with some legwork and will be happy to share my research method. One good technique is to look for additional spouses, as additional info is often included in subsequent marriage documents. I had two ancestors whose relevant (to my line) marriage documents claimed no known parents. However, in later marriages, after everyone who cared was dead I suppose, those ancestors finally revealed their true parentage. Likewise, prior/first marriage records of females who were widowed are a good source of information (especially in Coahuila), as those females’ parents are not always listed in subsequent marriages. And, of course, in some jurisdictions the baptismal records will list grandparents. Good luck to you.