Besides Scott, the Stanley Gibbons Part 15 (Central America) and Part 20 (South America) could be invaluable. Also I have found Yvert & Tellier more useful then Michel.
If you can ever find a copy of the old Minkus Latin America, Volume 1, Part III buy it. It contains both Central and South American countries. Mine is 1980.
Most Latin American countries have their own specialized catalogs. Check the collector's clubs in the countries to find out what is available.
In my area (Colombia, Ecuador, Venezuela)Colombia
Alvaro Barriga catalog (1980's)
Leo Temprano 1984
The new catalogs do not have any detail.
There are a number of specialized air mail catalogsEcuador
Bertossi ( just found out about this one)
Banco Central in Quito, Ecuador for the small book about the first issues.Venezuela
Aurelio Blanco Catalogo Especializado de Estampillas
) for articles on classic Venezuelan stamps.
The specialized catalogs are usually in Spanish so I hope you can at least read Spanish. To make your life more difficult Y & T is in French.
For a friend I created a list of the catalogs available for each Latin country. I have to see if I still have it. If you are an APS member contact the APRL and they may be able to tell what catalogs are available for each country. They are really helpful people.