Here’s a quote of Drain from “No More Silence” by Larry Sneed, pages 259-260:
Over the years allegations have been made about the way the FBI and the Dallas Police Department handled the affair. In one of the books, I was quoted in a footnote as saying that I doubted that a fingerprint had been found on the rifle as claimed by the Dallas Police Department. As I recall, I think my comment was based primarily on our experts in the Single Fingerprint Bureau. That’s the real specialists in fingerprints in the FBI in Washington. From the time they turned the rifle over to me along with other things, they were placed in a box and sealed. I then took it to the laboratory where it was taken apart and examined with different processes on every inch of that gun, assembled and disassembled. They said that they didn’t find any fingerprints. Now, I wouldn’t have any way of knowing from my own personal observation. My comment would have been made on what they said. As to Lieutenant Day, I’ve known him a long time, and I think that he’s an honest individual. If he thought that there was a print there, whether there was or not, he was sincere in what he had to say. I would not want to cast any reflection on Day.
And the “devastating article” you posted the link to is just a bunch of questions. I don’t see how a hair or fiber of some sort trapped under the lift is supposed to be an indication of fakery.
You should read your quotations more closely:
"Over the years allegations have been made about the way the FBI and the Dallas Police Department handled the affair. In one of the books, I was quoted in a footnote as saying that I doubted that a fingerprint had been found on the rifle as claimed by the Dallas Police Department. As I recall,
I think my comment was based primarily on our experts in the Single Fingerprint Bureau. That’s the real specialists in fingerprints in the FBI in Washington. From the time they turned the rifle over to me along with other things, they were placed in a box and sealed. I then took it to the laboratory where it was taken apart and examined with different processes on every inch of that gun, assembled and disassembled. They said that they didn’t find any fingerprints. Now, I wouldn’t have any way of knowing from my own personal observation.
My comment would have been made on what they said. As to Lieutenant Day, I’ve known him a long time, and I think that he’s an honest individual. If he thought that there was a print there, whether there was or not, he was sincere in what he had to say. I would not want to cast any reflection on Day."
So, it wasn't actually Drain's opinion, it was the opinion of the "experts in the Single Fingerprint Bureau."
And the “devastating article” you posted the link to is just a bunch of questions. I don’t see how a hair or fiber of some sort trapped under the lift is supposed to be an indication of fakery.
Your analysis of this article is as weak as some of the counter-arguments you've put forward.
I would urge any reader interested in the investigation to have a look through some of the questions that really do need answering:
https://docs.google.com/presentation/u/0/d/12LFwzP_tXUVE5tMM-qekgfYiL1PQK4L5H-aQ2Dmk0SE/htmlpresent?pli=1