Contact Witnesses Soon

Contact your witnesses soon. Do not wait for the insurance adjuster to contact them first, because he makes a living by turning situations into support for his company's position. He is trained and knowledgeable in putting testimony into the minds of witnesses and getting them to agree with a certain version of purported facts.
You should be the first person to call the witnesses. If you are too injured to call, have a family member or friend make the calls for you. Make the contact as simple and unobtrusive as possible, explaining your circumstances and stating that you are seeking their help in knowing and documenting what actually happened.
Be sure to let witnesses know that they are under absolutely no obligation to speak with the insurance adjuster. They can tell the insurance adjuster that they have given a written statement to the police, for example. You don't want to instruct them not to speak with the adjuster because that may constitute interference, and you want the witness's testimony to appear objective. More than that, you want their testimony to be objective. You might, however, tell them if they choose to speak with the insurance adjuster, they are under no obligation to be recorded. They may choose to tell the adjuster to just jot down their comments and write it up, sending it to them for a signature.
If they agree to be recorded, you could tell them they have a right to get a copy of their statement and that it would be a good idea to come to an agreement with the adjuster on that prior to being recorded. You can ask them for a copy of their statement after they receive it. There is nothing wrong with their giving you a copy of the statement that they have given to the insurance adjuster.