Contact Marlene Jenkins, mjenkins@mdsp.org 410-653-4247 and first see if the gun has already been submitted by someone else. If not, Ms Jenkins can email you the forms. fill them out and send them along with a handgun to the board. Yes, a FFL can ship the gun to MSP even if it isn't on the roster. Marlene can assist. BTW, I do not know if she has any additional staff, it may just be her in that one office, so it may time a few days for her to respond.
Sometimes a physical handgun sample is not required. I just recently went thru getting a model added that was not on the list. As it was very similar to an already approved model from the same mfg a sample was not required. I was pleasantly surprised at how relatively painless the process was, although it took a couple months so you can't be in a hurry.