Whereabouts are you? We have a lot of local shows which, some of which do have crossbred classes, we usually try to show a zwartbles cross lamb each year. Much easier to prepare than the purebreds as they don't need trimming etc, just need to look tidy, as we only breed a couple of ewes for crossbred lambs so don't have many lambs to select from I am pleased that they generally do well showing.
The best lambs usually stand out in the group, but they need to be correct in their mouths and feet/pasterns etc also.
You could go along to a local show to watch first or just enter and see how it goes and treat it as a learning experience to see which sheep are well placed.