From what you have described, the original work may have been done by the shotcrete process or hand-applied. Typically in the shotcrete process, over a large area at the thickness of 5 in. (127 mm), you would expect to see reinforcing mesh or reinforcing bars.
The material can be patched. If the areas are small, it may be prudent to hand patch. Shotcrete is most effective in larger applications. It is important to select a good repair mortar or mixture design.
ASA does not have a recommended finish. Generally in this type of application, the goal would be to match the existing surfaces as close as reasonably possible.
Many patches are done on bridges and other structures without regard to water penetration.
We do not have certified contractors; however, many of our corporate contractor members have ACI Certified Nozzlemen on their teams and the Buyers Guide on the ASA website can be searched by location and specialty. Also on our website, we have a position paper on “Shotcrete Contractor and Crew Qualifications” with a handy checklist summary that would be useful in qualifying potential contractors for your project.