Maybe what I do will help. Firstly, doing the heel/toe thing is to me much different with a G25 than it is with my real car.
So I cheat....a little. I keep auto clutch on, but select shifter, and still using the clutch manually, It is like having training wheels on a bike. Eventually, you can take them off and ride (or in this case, blip) just fine.
Try it!