Recently, it has been proven that light can be squeezed into metallic channels with subwavelength lateral dimensions. Here, we present the study of the propagation of channel plasmon polaritons confined in gold V-grooves, filled with fluorescent particles. In this way, channel plasmon polaritons propagating in nonempty V-grooves can be characterized, as the propagation track can be directly visualized in the microscope. We have found that beads with subwavelength diameters act as frequency converters for the propagating channel modes, resulting in larger propagation lengths. For micrometric-diameter beads, we show the possibility of individual excitation, what may have applications to develop very sensitive biosensors.