Total Groom by Lincoln, not expensive, repels dust, gives a nice sheen without that slippery texture that transfers onto your hands.
Use it a few days before a show after you've bathed or use as you groom instead of bathing, or a good spray over the coat ( if you lift the hair by brushing the coat the opposite way) then bob a spare fleece and it will lift the dirt/excess grease out of the coat and transfer onto the inside of the rug.
Nothing beats a natural shine from a good diet and elbow grease