I wouldn't. Lawyers typically don't charge a retainer, so why not let the lawyer work on the early part, so you can best ensure you don't screw it up and damage your overall case? Some claimants decide to wing it on their own, because of that slim chance their records are stellar from the getgo and they will win on initial - which means they can avoid the legal free withholding. That is a valid decision, of course. Money talks. However, they also increase their chances, if their evidence is not "all that" as required by SSD law (and the claimant has rarely studied the law on what is required), that they will not only lose on initial but they will lose on appeal - because sometimes early damage can not be "undone". For this reason, and yes, I am biased, I recommend NOT being penny-wise/pound foolish, and retaining that zero retainer, dedicated SSD lawyer before you apply, if possible. If you have already applied, I suggest getting one now, to jump in and take over.
*Note that there are many lawyers that are not willing to do that early work, and will only take your case after you have lost once or twice. However, there are MANY in the U.S. that will, so make sure to inquire and don't give up if you receive some No's. Many of us actually prefer to take cases from the beginning. And, despite popular misconceptions, and a little bullying from local attorneys, you need NOT retain a local attorney - SSD is federal, not state, and it runs on paper and technology, not on face to face interactions. The only face to face that MAY end up occuring with need is your face in front of the Judge, and the Judge has video technology so that your lawyer can be there also, but you don't have to pay her travel expenses. Technology has helped many clients NOT have to be constrained to use the local yocal that has little SSD experience, or is a "jack of all trades", or the lawyer that is rude or non-communicative, because he is the only lawyer accepting SSD cases in the area. The U.S. is your oyster, so get out there and pick who YOU feel comfortable with, don't feel bullied into a local lawyer because he says you must.