[Mazda]

If it is an ordinary plastic kit, I would use Revell Contacta. I find it dries and hardens quickly. It also has a fine tube for applying to small areas.
For filling I use P38 car filler for larger areas as it is easy to apply and sands well. For a finer finish and small blemishes Humbrol model filler is good. It dries quickly and has a very smooth finish. I use an old credit card to apply filler as it can be easily cut down to apply filler in very small areas.