Remember that no translation is perfect. The minute you begin to render your first sentence, the original is already lost in translation. It is your job not to find an equivalent but rather reconstruct the original as though it was written in the target language. Cultural concepts, shades of colour, shades of meaning, and even history can and will be lost. Don't be afraid of that but instead embrace it. You can always use footnotes / end notes if necessary. Who is your audience?
Proofread the translated finished parts one by one before the general read and review at the end. You might find a better word or an expression in the same language that gets the exact meaning of the other. Do not over process, but check to see where can you install your enhancements.