I guess you would need access to hemp flowers (bud). You would get about 3-4% CBD in hemp with less than 1.5% THC. Female hemp is generally used for seed/oil production and males for the fibre (at least thats my understanding) so due to the percentages and the fact that hemp flowers are generally seed laden you would have to process really large amounts of flower to get a return. In theory if you grew hemp on your farm or something and took the time to kill the males you would have a better yield of extractable material. In that case my process would be grow-harvest-cure/dry and then beat the flower end against a large screen like the hash makers in Morocco. Then I would run a solvent extraction on the powder (hash), filtration and distillation for a final oil product. Your enemy is likely going to be the amount of material you have to process.