Once a week I remove all of the hammocks and toys and place duct tape* on the ends of my cage and place it into the shower for a good scrubbing with dish washing detergent. I purchased dish/pot scrubbers that have a handle on them to use to scrub out the crevices. I have the plastic needle point canvass stuff on all of the floors of my cage. (Periodically, I replace it with new since my girls love to chew!) I rinse well and place it on a large towel in my hallway. After drying it with a towel, I put everything back together with fresh bedding and clean hammocks! Inbetween these weekly cleanings, I sweep the floors clean and wipe them down with a hot soapy cloth, followed with a fresh clean wet towel to give it a rinse. Water bottles and food bowls are washed and replenished DAILY. I am a stickler for that! All uneaten food that I've given my girls the following morning is removed from the cage. Also, there may be times that I will replace a hammock or two (I use several) when they become soiled a little more than usual. Once a week is just about right for my girls. It does depend if you have boys though..they can be smellier! And it also depends on how many rats in the cage..of course.
It can be hard at times, especially to life the Martins 695, but I use the handles that came with it. I just make sure everything is set up in the shower before I walk out of the rat room with the cage. (And I have to be sure I close the door so my cats stay out!)
*thanks for the idea Papercrow! It works great!