1) I don't callous the ends, it's not necessary.
2) On suggestion from others, I started to use a 10% bleach solution for a while, but I'll be honest, as long as you respect a few things, brush your cuttings with a clean toothbrush and some dish soap, don't constantly open and don't touch your cuttings/paper towel, it's not necessary to bleach in my opinion ... I don't bother with bleach anymore.
That said ...
Three most important things to respect: Moisture, cleanliness and airflow.
Moisture: Almost no moisture is required in your paper towel when using the baggie method. Leave the butt-end of the cutting bundle uncovered by at least an inch and wring out most of the water (clench with one hand to squeeze out enough water) - the goal here is NOT to cover the cutting completely, the paper towel is simply to generate relative humidity (thus not much water is required). DO NOT water the rooted cutting into a pot, that's too much water - pre-wet your potting mix to the point that it is like a dry cake that barely holds form when you squeeze a wad in your hand. DO NOT leave excess water in the bottom fo your bag or rooting bin, and wipe up any large water drops (fine mist is OK).
Airflow: By leaving the butt-end of the bundle uncovered by the paper towel, you are promoting airflow into the bundle AND you can see most root development. Open the bag and allow fresh air into the bag every couple of days (careful not to spit into the bag if you're blowing air in, you have lots of bacteria in your mouth). When transferring to pots and your rooting bin, be sure to crack the bin daily and allow the cuttings to breathe.
Cleanliness: If you absolutely have NO CHOICE but to touch your papertowel and/or cuttings, be sterile ALWAYS! Wash your hands with antibacterial soap before and during initially wrapping your cuttings - wash your hands before touching anywhere inside the bag - don't leave your clean paper towel on a countertop, nor your cuttings (treat everything like it's a mold factory) - handle your cuttings bundle as little as possible - any time you must take the paper towel out of the bag, NEVER reuse, always get a new paper towel.
I'll be honest, using the old paper towel + baggie method, I'm lucky to have 50% success getting from stick to tree, although I'm normally achieving a good 90%+ root strike. That method of rooting has its problems for sure. The 'alternate baggie' method has produced much better results for me. Link: http://figs4fun.com/Rooting_Bag_New_Style.html (note the product number of the baggies is on the label in the bag picture).
Also, if you haven't seen the original/improved baggie method Jon originally shared with CFRG, please re-read: http://figs4fun.com/basics_Rooting.html (skip the "update" link, I just posted it last paragraph).