For adult igs I've always used blue jeans for transport. I use a strong cord to close the pant-leg just above the cuff. Then I put the pants on the floor, hold the waist up so the closed pant-leg looks like a tunnel. Most times, igs walk right in. Then I use another cord to snug up the pant-leg just behind the ig's rear legs. They strain to get out, and make deep and loud sniffing sounds, but they always travel well this way.