It took 8 months of suppositories to get my cuffitis under control. I have UC and thought the same as you do about canasa as it is the same mesalamine ingredient that I took orally via Asacol for 14 years. That failed as I had to have my colon removed! The suppository is putting the medication directly into our j-pouches and it doesn't have to travel through our entire digestive tract to get there.
I first used anucort for several weeks then canasa and back and forth until my GI sent me to an IBD specialist who told me to take canasa until it worked. He also said to use anucort in addition to canasa on breakthrough days. Canasa at night and anucort in the morning - or vice versa. Just not at the same time.
I was upset by all of it as I thought the operations were going cure me 
I still use canasa almost everyday and anucort when I can tell things are more inflamed. He told me that some people use it several times a week to keep it in remission. That didn't work for me. I can skip it sometimes for a few days but hate flair ups! I use surgical gloves and personal lubricant which makes it almost like brushing my teeth. My take down was 4.5 years ago.
I'm sorry that you have crohn's now 
I agree with everything Scott said - especially about trying one new thing at a time. Sometimes things are so bad that we have to use several right away.