Waterslide transfers are easy to use and is a great way to detail the hard to do parts.

Cut out the decals that you want. You can slide straight onto the substrate and it dries to substrate OR for a stronger joint I use matt varnish and paint to area for the transfer. Soak decals in warm water for about 20 seconds wait until the decal slides on the backing card then place in position on model ..... on the wet varnish and put out the backing card so transfer sits onto the model. Reposition if needed and dab dry. Leave to dry and harden.

Using the wet matt varnish gives a good mechanical join and allows for good adhesion more resistant to handling.

Once dry touch up paint on model if required.