I know some people brush (you can get a child's soft toothbrush) their longhaired hamsters everyday, but I rarely do it, Twinkle manages to groom himself perfectly fine. As they get older and less mobile you may need to help them a bit more with brushing or if you see bedding getting tangled up in the fur.
You might like my thread about Twinkle, my long haired white syrian, you can see how short/flat his coat was in the photos/videos to start with, then one day he just turned into a fluffmonster.
Introducing Twinkle