NEW YORK/SAO PAULO—Coffee experts working for commodity trading houses are taking to the narrow, winding roads in Brazil’s Minas Gerais state as they tour the coffee belt checking 2022 crop prospects just as prices approach the highest levels in 10 years. This has been a difficult year for coffee farming in Brazil, the world’s largest producer. Prices surged after a drought and later frosts ruined as much as 20 percent of coffee trees, hitting future production. So far, those studying crops have produced wide estimates for the 2022 harvest, though traders for now are still betting on a less fruitful crop. The people walking the fields will find the truth of that between now and the end of January, the optimal time for crop assessment. “The rains that followed the frosts and drought produced a nice flowering, but now we have to see how many of those will grow into …