Race Track is the easiest way to get down from Little Rainbow. The upper part has tight turns, the lower part opens up more. There is a set of switchbacks lower down that are pretty steep for a beginner trail.
Race Track gets uphill traffic so look ahead and share the trail.
If your goal is to go east to west on Little Rainbow, Race Track is probably your best bet to get there. It's uphill, but only has a couple tough climbs.
Don't forget to stop and look at the Castle Gardens area as you pass. Amazing views!