To answer your main questions first. The speed of other papers in comparison to HDPP will almost certainly be different, it will probably be faster, but could be slower, and the only way to find out (if there isn't a data sheet available) is to make a test strip - a series of exposures, on a strip of paper if you want to save paper. This can get a bit tedious and time consuming the first time, but ultimately it's going to save you time by not having to randomly guess exposures.

It will placed so that its emulsion to emulsion. The emulsion should be the dull side, as the paper is normally white, but you might not be able to see that if you don't have a darkroom & safe light. Whilst you should avoid touching the paper surface, you can usually feel the difference. Also HDPP curls down, the emulsion is on the concaved side. Resin Coated curls up, the emulsion is on the convexed side.

To answer your update, I'm not sure I understand what you are trying to do, it seems like you are making some test exposures without a paper negative, to get an rough idea of exposure times? Bear in mind that the exposure with a negative will be different, and each negative will have a different exposure.

If you are developing normal negative paper, and it's black, then it's over exposed. (HDPP is the opposite - black when unexposed, and white when exposed).

I'm not sure if you were trying to make a contact print in camera with daylight/torch, or trying to make a contact print without the camera, and just take the camera apart and expose the tray.

Personally, I wouldn't use daylight to make prints, as it's to variable. If you are doing this in camera on the Pinsta Pro, and the negative paper is turning black within a second using a torch, then look for a less bright light source.

Tim, thanks for your response. A few things:

To answer your main questions first. The speed of other papers in comparison to HDPP will almost certainly be different, it will probably be faster ....

Yes, I want to do a series of tests to get the right exposure times for the Arista paper.

... place it so that its emulsion to emulsion. The emulsion should be the dull side ....

I get that when I'm making a contact print (using the Arista paper as a paper negative) that it should be emulsion to emulsion. However, I found that the emulsion side of this paper is a bit shinier. That's specific to the paper I assume.

... I'm not sure I understand what you are trying to do, it seems like you are making some test exposures without a paper negative to get a rough idea of exposure times?

Not quite, sorry for the confusion. I was attempting to greatly overexpose and underexpose the Arista paper to see which accounted for my very dark print. What was happening is that both of these resulted in near-black prints, and that's what I was describing. I was a bit rushed, so not very 'scientific' about my tests. As an afterthought I wondered if I was developing in the fixer by mistake .... but no worries, because as you said

If you are developing normal negative paper, and it's black, then it's over exposed. (HDPP is the opposite - black when unexposed, and white when exposed).

That pretty much answers my question. I assume then that my 13 second exposure was way too long. I have the Pinhole Assist app and it has various papers or films I can input to get different exposure times. I'm not remembering what settings I used, but it gave me an initial exposure of 3 seconds. I second-guessed this and added 10 more seconds ... which was a mistake.

I was thrown off by the vast difference in times between the HDPP and the Arista paper. I assumed there would be some difference, but it seems the Arista is much faster. As you said, they are different, and I need to test, test, test.

I'm not sure if you were trying to make a contact print in camera with daylight/torch, or trying to make a contact print without the camera, and just take the camera apart and expose that tray. I am not using daylight. Once I get a decent paper negative I want to us the Pinstra to then make a contact print on the very same (or a different) paper, using a flashlight as my light source. At this point, - and similar to the tests for the paper negs - I'll have to experiment with how long an exposure I need.

Martin at Pinstra recommended a 1000 lumen flashlight (torch) for 'flashing' the HDPP. I have a 500 lumen flashlight, so I'll have to experiment (and test, test, test) a) how long to 'flash' the HDPP, b) the exposure times for the Arista paper, and c) exposure tines for contact printing in-camera.

All the best, David