I don't use tubs!
For my glass tanks I use 50W red bulb, digital thermometers from Petsmart, and this thermostat from Amazon
http://www.amazon.ca/Jumpstart-Digit...rds=thermostat
Which has dropped in price, by the way! Almost by half

I might up the wattage to a 75W or 100W when I upgrade my ball python to a larger tank. He's in a 15 gal right now.
With my UTH set at 89F it ranges from 86.5-91.5F on crazy days, but usually 88-90.5F.
You may have to tinker with things as well; trial and error. I know that's not the answer you're looking for, but everything is different for everyone - what your home's ambiet air temp is will change over the seasons, which may mean you will need different wattage bulbs for different times, regardless of if it's a CHE or red/black bulb.
You will find a rhythm, don't stress too much. Research is key, and you're on it.
Best of luck!