Slipping jabs and crosses, bob and weave as many other shots as possible.
Slip a jab and follow with your own right straight over the top of that and you should land it whilst covering the distance on him. Won't work if you arent too fast on the old reflexes though.
Bob & weave say hook punches but attempt to close the distance with them also otherwise you'l be standing in one spot still out of range.
If you'v done any points fighting kickboxing or freestyle karate, I would say the most effective way of covering the distance to take away the reach and awkwardness would be a blitz. Search up Raymond Daniels points fighting or Michael Page videos on youtube for that though.
Hope it helps!