This study experimentally investigated the net benefit of film cooling with six rows of impingement–effusion structures on the suction surface of a vane. The experiment obtained the film cooling effectiveness of a double-walled system on the suction surface via the pressure-sensitive paint (PSP) technique. The film cooling effectiveness obtained by the PSP technique is coupled with the transient liquid crystal (TLC) technique to determine the heat transfer coefficient. This combination of techniques reduces the time required for the experiment and improves efficiency of the experiment. Through the experimentally measured film cooling effectiveness and dimensionless heat transfer coefficient, the net heat flux reduction (NHFR) is calculated to comprehensively measure the net benefit of film cooling. At the same time, in view of the lower net benefit of film cooling of the film holes in the front of the suction surface under a higher mass flux ratio (MFR), the study improved the cylindrical holes into fan-shaped holes and proposed two improvement schemes: Vane A and Vane B. The experiment was carried out under three MFRs (0.4%, 0.8%, 1.6%), and compared the film cooling effectiveness, heat transfer coefficient ratio, and net heat flux reduction of Vane A and Vane B with the baseline vane under each mass flux ratio. The findings show that using the coupling of PSP and TLC to determine the heat transfer coefficient can yield credible results. The improvement of the fan-shaped holes makes the film cooling effectiveness and heat transfer coefficient ratio improved compared with the baseline vane. Changing cylindrical holes to fan-shaped holes does not necessarily lead to a better net benefit of film cooling. The fan-shaped holes should be arranged reasonably to obtain the better net benefit of film cooling.