As with all painting there's an amount of preparation work to be done. For the badges that I re-painted it was as follows, firstly dunk the whole badge briefly once in hot soapy water and wash the whole badge with a sponge and then rinse briefly, while it's still wet carefully scrape away stubborn grime on the wooden base with a straight edge and leave to dry.
Once dry paint preferably with a reference to work from. Small tins of modelling enamel will cover about 4 badges. The colours gold, blue and white appear on most badges, too save time it's better to use larger tins for these colours.
These are examples of badges as they existed on the walls of Rubys before I paint them.
The bones of the British Navy Badge which is also the standard for the Royal Navies of the Commonwealth is the crown, nameboard and cable boarder
The crown originates from a roman design and should be gold the ruby, pearl, emerald and sapphire jewels should be the only other colours, the nameboard should be gold with black lettering and the cable boarder should be gold, it is very common to see badges with artistic license to make them appealing checkout ebay just type in 'hms crests'.