Heat adaptations come naturally if you regularly ride outdoors in the summer, and it is hot or hot and humid where you live.
To get adapted during Z2 rides, pacing by heart rate (e. g. sticking to <= 140 bpm) has the advantage that it puts a comparable load on you and you will get quicker with time. If you always pick the same route, you should be able to see that comparing your times. But make sure to give your body time to adapt.
The other key word you used, dry heat, is important. Dry heat tends to be much easier on me. Cooling is alright in the dry heat if you drink enough. But in Japan, heat is usually humid, and humidity can play a number on you. E. g. when you climb, you are moving more slowly through the air and cooling gets worse. I remember having to pack a second pair of socks to change into mid-ride. In the South it was so bad that even walking had me drenched in sweat in no time, and I had to wait until sundown to go running.