An old t-shirt does the job too if you can't find one :-D Not that my setter is ever in any kind of 'show ready' state :-o but her breeder used to use one :-)
I bought a drydog coat for the Golden at Crufts. It's brilliant. She dries without any sticking-up bits. Even the root of the tail goes flat. Their tel number is 01790 763574
Mine is a standard "medium" but the lady who makes them is very helpful and will advise for your breed. The coat needs to appear too long or it will not drop over the rump and you will get the hair of the root of the tail sticking up. Make sure you brush it as flat as poss before putting on the coat then leave until completely dry.