If protocol and reagent are fine then you will get good efficiency. Serum starvation enhances efficiency. Prefer not to use any antibiotics during transfection. As Sundeep suggested that efficiency will depend on the cell to cell. You will need to work on lipofectamine reagent volume since its causes toxicity. Fugene has a single reagent, there also needs to be work on the volume required to transfect efficiently. For electroporation, buffer preparation is crucial. Polyplus transfection reagent is also there which works very nicely.

DU 145 is not a cell line with high transfection efficiency. Mirus Bio (now part of thermo I believe) has very good reagents that work well with the PCa lines. I would suggest looking into this line of products.