Just start with insufflation. ~30 mg is a good place to start. It's a mild dose.
A little trip report on 8 mg.
IMPORTANT UPDATE, Nov. 14. There are doubts expressed on SoS that this cinnamon-coloured powder sold by this traditionally reliable Canadian vendor is pure DPT. That despite the statement and link on the vendor's website that claims 98.7 percent purity (HPLC). Based on lack of solubility of the HCl and lack of homogeneity of the powder (I tested neither), there is speculation that it contains large amounts (up to 80 percent) of a pre-cursor, unreacted indoles or other unidentified gunk, in addition to the DPT. If true this would be hugely disappointing from this vendor. Until the issue is settled, the below trip report is thus to be seen cautiously as to whether it constitutes a pure DPT experience. I don't share however claims on SoS that this powder is borderline inactive. Given my satisfying experience on a low amount, see below, the powder is clearly active.
T minus 1 hour: opened package, in the mail from a traditionally trustworthy Canadian source and poured the substance into a glass vial for long term storage. Noted that the powder is denser than 2c-x, one gram is a small quantity. Also noted that the color is a faint brownish powder. Unsure if that's the normal color or an impurity. (Edit: it's possibly the same "cinnamon" powder referred in posts above.)
T minus 30 minutes: Erowid writes that the threshold dose is 5-20 mg insufflated. With that wide of a range, I decide on 8 mg. I consult the "Guide to insufflation" on Bluelight. That was necessary because my one and only other attempt to insufflate (5-meo-dmt) was unpleasant. The guide helpfully writes that insufflation should be done lightly to avoid a drip down the esophagus. Feeling thankful, I press the "donate" button.
T minus 20: I verify my precision scales are working accurately and measure out 8 mg. A few small specks. I cut a plastic straw in half as my tool to insufflate.
T minus 10: usual precautions. I ingest a capsule of grape seed extract to protect the brain from the free-radical releasing effects of psychedelics. And an aspirin, to thin the blood so there is less stress on the heart from any blood pressure effects. Plus a raw clove of garlic, just because my grandma would approve and it's healthy. Also get out the Cyproheptadine in case it's needed for in an emergency of serotonin syndrome.
T minus 5: I make sure the setting and mental state is good. Psychedelics and I get along very well. They reliably elevate me towards light, love, empathy and insight. Phenetylamines and I get along particularly well. Tryptamines and I get along ok. I remind myself that whatever happens on the trip is a reflection from inside me and my subconscious. The iconoclastic image of Dr. Freud comes to my mind. Or the trip may hold me the mirror of my "shadow" to my face, as tryptamines sometimes do, which would make for a more difficult journey. I surrender to those when they come but don't seek them out. An image of Dr. Jung comes to mind. It's all good.
T: I insufflate 8 mg. No issues.
T+30: Plus one on the Shulgin scale. I am pleasantly surprised how natural the come-on feels. The come-on from the phenetylamines or even 4-aco-dmt feels more chemical than this. (For completeness though, magic mushrooms and I get along, but are not great friends.)
T+40: the pleasant merge of soul and mind I love with the psychedelics is happening. A feel of connection, empathy, love. I spontaneously start a chat conversation with a stranger half across the world about God and the Universe. That is unusual for me because I more typically enjoy my journeys the same way Terence McKenna did: alone, silent and in darkness.
T+150: I feel I'm past the peak. Plus 2 on the Shulgin scale. I decide to go to bed.
T+180: lying in bed consciously, the effects linger. Feeling in touch with myself and others. I happily drift to sleep.
T + 9 hours: I wake up and note effects are still there. No hangover, just not back to baseline.
T+11 hours: still not returned to baseline. I am unsurprised as journeys tend to linger longer with me than what Erowid suggests. Erowid places an upper limit of 8 hours of total effect.
Bottom line: This was a pleasant and elevational trip, surprisingly natural feeling. Apple pie stuff. DPT and I get along very well. Next time, I'll titrate up to 10mg. My habit for all powerful psychedelics is to start at a treshold dose, and titrate up 2mg at a time.