If you can afford to do so, buy all the guns at once. When you send in the Form 4's enclose a letter saying why you are buying so many and I don't think there will be any problem. (You can check with BATFE in advance if you want.)
Then, assuming there is no change in the law, sell those you don't want one or two a year as you would do normally in weeding out a collection. I think it is a sure bet you won't lose money.
Or use a dealer, as suggested, but that will add $200 to each transfer.