Dumbo rats are to be raised the same as normal fancy rats. Dumbo's deffinetly come across a little slower but are more calm and affectionate then standard eared I have found. Rats come in many, many coat colour variations and coat types such as standard, satin, rex, double rex and hairless. Rats even come in tailless (which is rare).
They need to have rat friends, no matter what anyone tells you, they are very very social and should be kept in pairs or more.
Male rats are larger and often calmer, they have a more musky smell and tend to mark more. Male rats can be nutered and housed with females, which also reduces their likelyhood of sexual cancers and helps with odor and marking.
Females do not have much odor, mark less and are very energetic and acrobatic.
I have always had female rats and have always kept them in groups.
rats need to have an appropriate sized cage as they need room to move around well, and love to have boxes, bedding, hammocks and fun treats and chewies. Out of cage time in a secure area, and time spent with their human friends is always a cause for excitement. Be aware that they will chew things if they get bored while outside of their cages.
For more rate information there are several online websites providing lots of information.