Tirwin
You can use an infrared scan gun to quickly check rotor temps. As I said the Pagid folks like to use a pyrometer. If you already have one just use that. The trick is to do it quickly as brake rotors cool very quickly.
Be careful of asymmetrical cooling.
"Another type of cooling problem is an imbalance between the inner and outer faces on the rotor. Andreas Boehm of Pagid feels too many people have a brake duct that only directs air to the inboard side. You really want to “force cooling air into the eye of the rotor and out through the vanes. If the rotor temperatures are asymmetrical the brake paint will display this by being different on the inboard side of the disc from the outboard side of the disc.”
Once you measure the rotor temps you'll realize that you really don't need to spend money on cooling.
I might also flush the entire system with denatured alcohol before I take everything apart. Then when I add the new fluid there is no residue left in the lines.
Richard Newton