Without getting into specifics you need to train during winter to build you base speed. A combination of endurance, speed endurance, speed work and plyometrics will all aid you in improving your times. Naturally you will have to work your hurdle drills at least twice a week. (normally when you do your speed sessions)
In terms of technique and going to 3 stride – the most common problem is athletes not driving over the hurdle, floating, then breaking by planting the foot out too far in front of their body mass as they come down, causing them to slow and making it hard to run to 3 strides. Work on attacking the hurdle and driving over it. As your lead leg's foot goes over the hurdle snap the leg down hard and throw your elbow back pulling your trail leg through (dont worry you wont hit the hurdle with your lead – momentum ). This will limit the floating and increase your push thru to your next stride.
A drill to use is place something like a cardboard cutout stuck to the top of the hurdle only 5cm high and try to hit it with your lead leg, but dont strike the hurdle, again this limits floating and going too high. – Good luck and train hard!!