Turn it between centres! Bushes are handy, but not fully necessary. If I have bushes for a kit, I will use them for getting good roughly to size, if not I use some outside calipers - one set for each end. I attach them to my headstock and tailstock with magnets, so I don't get them mixed up.
It takes a little practice, but it is well worth it, especially with single tube kits - no chance of bending a mandrel!