Azureus were imported into the United States by two individuals Nabors and Watley. The Nabors line were the regular spotted frogs and the Watey line were finer spotted frogs. The different lines have been in the country for several decades. The two lines are from the same area in Suriname they are found in only one forest area isolated by large areas of prairie. Some have bred to maintain the separate lines of frogs Joshsfrogs.com carries the Watley line of frogs.
So, in answer to our question, yes you can cross a fine spot Azureus with a regular spot. Some have bred for special traits such as no spot and fine spot by inbreeding which you want to avoid but crossing with a known separate line of Azureus would help strengthen the genetics of your frogs. Also any breeding pair of Azureus can produce fine spot offspring they are just not as common as the regular spot fogs.