Seems like you made up your mind. Let us know how things turn out.
Again, I feel almost like I'm doing something wrong by advocating DIY impressions. PLEASE don't do this if you don't feel comfortable with it or haven't at least had a professional do it for you more than once. The last thing I want is a bunch of people shooting silicone into their eardrums, suffering permanent hearing loss and blaming me for it.
I understand the risks... I understand the WORST CASE SCENARIO, but I also understand taking precautions, being careful and thinking things through. Ear impressions aren't rocket science. I can tell you what COULD happen when you go out and get in your car: things far more worse than a perforated ear drum. But if you're smart and take precautions, you'll be fine.
I received my gun (bought a 50ML gun and 50ML cartridges), heavy-body silicone (high-viscosity) and tips in the mail. Having had a little practice, I'll never go to an audiologist again. Total cost: $32 (gun was $10. Came from China so it took around 3 weeks to get here. 2 cartridges of silicone with 6 mixing tips were $22 from a seller in the US). After making a few impressions, I wouldn't expect anymore than 5 impressions per cartridge of silicone.
For the record, I've been cleaning my ears out routinely while waiting on the materials to arrive using a vinegar/alcohol mixture and ear syringe, to ensure there was no wax buildup.
I made the cotton dams myself with pieces of cotton and dental floss the same way my audiologist does. I experimented with the size of cotton as I was a little worried the silicone might get passed the block, so I basically used as big a piece of cotton I could tolerate. If it was too easy to get into my canal, I pulled it out and started over. Better safe than sorry. Again, having been to an audiologist many times, I already had a feel for this procedure. I used an IEM case for a bite block. It was about an inch thick. Maybe a little more.
It definitely takes some practice to get this right. There is a technique that is learned when you've done enough of these. I wouldn't expect to get it right your first time. If I could do it again, I would probably buy one of those ear impression syringes and 2-part silicone putty. It'd definitely be easier to handle. With the gun, the trigger has to continually be released and pressed again (maybe 4-5 times during each impression) and each time you cycle the trigger, it's hard to keep the nozzle in place. What I learned was holding the nozzle with my other hand to help guide it while I cycled the trigger made things easier. Otherwise, the gun jumped each time and took silicone with it. It was quite messy. Even after this steep learning curve, my very first set was almost PERFECT. The only mistake I made was not overfilling my ear. This is very important for making the faceplate. I filled all of the critical parts INSIDE my ear, but didn't overfill to allow them extra material for the faceplate. This was easily remedied after the impressions had hardened by simply adding silicone to the outside and patting it flat. You can likely tell what I mean by looking at the pictures.
Also, the silicone I got was REALLY sticky. If you touch it, it WILL stick to your fingers. I cut small pieces of parchment paper, placed it on the wet silicone and lightly patted it when adding the silicone to my original impressions. Another tip: it's better to use too much silicone than not enough. It's easier to make the impression when you're constantly squeezing out silicone keeping a steady flow of it. Once the silicone stops flowing, I found the tip would sometimes drag the material. Just keep pumping the stuff and try to direct it towards all the tight spots without really submerging the tip in silicone. As long as you get it close, the stuff will expand. Again, it takes practice.
Removing the impressions was definitely unpleasant. This high-viscosity stuff dries much harder than what my audiologist uses. Therefor, it doesn't flex as much when removing them. Opening my mouth and twisting the impressions helped, but only a little.
The finished results on my first try AFTER adding silicone to the outside are as follows:
Honestly, I think I may have done them better than my audiologist.
UPDATE: I'm finding that the silicone is easier to handle at a cooler room temperature. I made another set today and it was a complete mess (though, to my surprise, the impressions came out 100%). My apartment was particularly hot today and it's almost as though the silicone melts at warmer temps, so the stuff was sticky as hell! I let the silicone surround the tip a little too much and next thing I knew, it was sticking to the tip more than my ear. I got it on my shirt, on the gun handle... when I pulled the gun away, what was still stuck to the tip, fell down my face. It was very frustrating. When I made the second set, my apartment was cooler and the material was very easy to use. Just be aware of the temperature.
