As you suggest, it takes very little to block the low speed fuel passages. The usual problem is a speck of sealer they use on the welch plugs in the carb housing. This was more common in years past though. I haven't seen any sealer present on any of the newer Walbro or Walbro clone carbs though it still may be present and out of sight.
I prefer brake clean over carb cleaners as the solvents are less aggressive and less apt to damage any rubber parts if present. Brake clean is cheaper also. Some of the new spray cleaners designed for cleaning EFI throttle plate assemblies are also advertised as being rubber / plastic safe so this would be acceptable. av8tor, I know you mentioned the carb cleaner issue, I just added some possible substitutes. Like many solvents, carb cleaners may have been neutered by the EPA these days and they my be rubber safe. I just don't take a chance on them as there are other alternatives.