Regarding stopping (seeing a red light ahead), I think it's best just to press on the brake (and alarm the people behind you), and when the engine rpm goes to near 1k, shift to neutral, and come to a stop; if the light changes to green when you are in neutral, you can shift into the proper gear, depends on your speed.
Making a fast turn using the heel toe technique is not easy. I haven't been able to do it well.
here's a write up from a Miata driver:
Beginning Heel-toe downshifting
By Kevin Morrison
I'm not really a Qualified Expert, but I can give you a summary of how I learned the whole heel-toe thing. For those who aren't familiar with the technique, it is a technique used in manual-transmission cars when braking and downshifting to match the speed of the engine to the speed of the transmission. For example, if you are downshifting from 3rd to 2nd when taking a corner, the engine will start at say, 3500 rpm and after the downshift, will end up at say, 4300. If you don't use your right foot to blip the throttle up to 4300 before you let off the clutch, the revs will have dropped to say, 2500 rpm and the clutch/transmission will have to "drag" the engine up to the required 4300 rpm. This is usually a somewhat violent occurrence which is hard on the clutch and more importantly from the performance driving standpoint, upsets the attitude of the car, frequently breaking the rear tires loose. The heel-toe part comes in when you have to be on the brakes at the same time you want to be blipping the throttle and this is where most people get lost.
To start learning to do this, I had to realize that the transmission doesn't care what the brakes are doing. Quite by accident, I learned that I could shift the tranny while also braking for a turn. I used to have to brake until I was slow enough for the turn, get off the brakes, and then do the shift before turning in for the apex. This takes way too long and I would often end up free-wheeling through the turn with my foot on the clutch, having to wait until I could straighten out the wheels before I let off the clutch (or the car would likely spin). This made me exit the turn way too slow and way out of the power-band of the engine. Once I realized the tranny and brakes don't care about each other, I started downshifting and braking for the turn at the same time. Once that was down, all I had to do was add the throttle blip to get the revs up before completing the downshift. The trick to the heel-toe throttle blip is in learning to manipulate the gas pedal while also braking, and maintaining a constant pressure on the brake pedal to avoid upsetting the balance of the car. This part took me a good solid year to perfect.
The term 'heel-toe' is misleading because most drivers don't really use their heel, but rather use the inside and outside part of the foot. To start, sitting still, put your foot on the brake (really just the inside edge of your foot) and then try to hit the gas with the outside edge of your foot. If you can't reach it, you'll need to either move the pedals closer together, get some "racing" pedals, or wear big clown shoes. Once you're able to hit both pedals with one foot, you blip the throttle by sort of rolling your foot over onto the gas while keeping constant pressure on the brake. Once you're confident about the motion required, start practicing while slowing down in a straight line (not in traffic, though!) with your foot on the clutch. Concentrate on blipping the throttle without making the car lurch around due to uneven pressure on the brakes. Once you can do that, start doing the throttle blip on downshifts. The sequence would be like this: brakes, clutch, shift, blip, release clutch, release brakes (when appropriate). When you get good at it, the whole operation becomes like one quick motion and you'll find that you can downshift in a fraction of the time it used to take...