There are optimized kits and protocols for SK-MEL 28 (https://altogen.com/product/sk-mel-28-transfection-reagent-melanoma-cells-htb72/) that should help reduce the need to test different concentrations to find an optimal protocol. With PEI there are many different factors that can lead to problematic transfections, and it can come out to be a costly assortment of concurrent setups. That being said, I'm sure there are PEI protocols for melanoma cells, and those should be generally applicable to your study.
There are optimized kits and protocols for SK-MEL 28 (https://altogen.com/product/sk-mel-28-transfection-reagent-melanoma-cells-htb72/) that should help reduce the need to test different concentrations to find an optimal protocol. With PEI there are many different factors that can lead to problematic transfections, and it can come out to be a costly assortment of concurrent setups. That being said, I'm sure there are PEI protocols for melanoma cells, and those should be generally applicable to your study.