I'm sure you've already noticed by now that the chemicals are by far the rarest material you will come across, often holding back progression on upgrades. Well this aspiring basketball commentator has the answer for you, I managed to get 600 chemicals in about 40 minutes.
One thing I'll add is that in the video he jumps on the horse to get further away, I found it easier to just run to the 2nd crossroads, took about 20 seconds in total.
Notes: This is not my video and all credit goes to the YouTube creator
Feel free to comment any suggestions