Once again, speaking from years of experience in this subject, there is only one way that has withstood the test of time and worked:
1- An adequate translator who is fluent in both the source language (German, Arabic, Latin, etc.) and the target language (in our case, English) and is willing to work on "unusual" subjects like alchemy/chymistry is located (this might take YEARS of testing translators until one is found) and who does not ask for exaggerated translation rates (0.01 to 0.03 $ per word translated is fine, more than that and it starts to get prohibitive even when several people pitch in to cover the costs)
2- People have to come forth stating that they are interested in the translation of any given text and will pitch in to help cover these costs
3- The person who finds the translator, or perhaps someone else assigned to assume the role of coordinator, if need be for someone with more familiarity with the literature of alchemy/chymistry and its specialized language/vocabulary, has to discuss any problems/mistakes that may be found in the first submitted translation with the translator and attempt to correct/clarify as many of them as is possible for a final more polished translation
4- A word count is made (this is very easy to do nowadays thanks to Microsoft Word's handy "word count" feature) of this final more polished version of the translated text and the translator paid his fees (this requires risk on the part of the person coordinating the project, as the initial money to pay the translator has to come from his own pocket; I have assumed this role myself a bunch of times, and yes, sometimes I end up paying the shares of some dead-beat bums who do not keep their word to pitch in to help cover the costs. Fortunately, the majority of people are not like that and do keep their agreements to share in the costs.)
5- The shares per person are submitted to the person coordinating the translation project, preferably through a quick and secure medium, like PayPal (sometimes I have received shares from contributors in the form of money orders or even cash via regular mail, but most people nowadays have access to PayPal accounts, so they prefer this method)
6- The translation is distributed via email among all those who contributed their share for making the translation happen (dead-beats who do not submit their shares are carefully noted, black-listed and of course banned from ever pretending to participate again in such projects as they are a threat to the whole effort and can actually end up costing the coordinator of the project some money from his own pocket)
PS: This exact same method also has worked very well in helping acquire photocopies/scans of rare and difficult to find books, articles or university theses on alchemy/chymistry.