Here are some 15mm Saxons are ready for painting.
All the figures are first cleaned of flash. Some of the figures had separate spears and shields. I usually glue these in place with super glue or epoxy before painting. Although this can make painting more awkward, a bare metal to metal bond is much stronger than paint to paint. Weapons and shields glued on before painting are much less likely to come off when the figures are handled during a wargame. If the position is such that pre-glueing will make it really hard to paint, I will leave shields and weapons off and paint them separately before glueing in place.
I then lightly glue the figures to small card bases with PVA. This gives me something to hold onto, avoiding rubbing off paint as the figure is handled in further painting . Bottle tops, blocks of wood and corks can also be used to give a painting handle.
The Undercoat. Undercoating is essential as paints will not adhere well to bare metal or plastic. I always use a spray matt white (Humbrol's Acrylic Matt White is my current favourite). I have tried other undercoating methods but for my style white is the only one that really works.
White brings out the brightness of the colour painted over it whereas a black or grey undercoat dulls the colour down. White undercoat also makes shading and highlighting virtually unnecessary. I use acrylic paint which has a slight translucent quality. If you apply it thinned with water the paint settles into the grooves on the casting giving a darker shade and the white undercoat makes the highlights lighter.
One issue with using a white undercoat is that when painting smaller scales (especially 6mm, but also 15's) not all of the detail is clearly delineated. To get around this I apply a very thin wash of Liquitex Raw Umber. The raw umber wash picks out the detail and makes it easy to block in the colours. It also provides a darker outline where the wash settles into the grooves. I find this unnecessary when painting 28 mm figures or larger.
See also My Secret Ingredient.
A very thin raw umber wash applied over the undercoat helps to delineate the detail and makes painting easier on small figures. This is better than a black undercoat as the highlights remain nearly white which aids natural shading.