I contacted the company from whom I had ordered oil and incense in early March. They informed me that the materials had finally been shipped today. It struck me that certain traditions consider Gabriel the patron of postal services, possibly confirming my intuition that their error was actually a positive sign.
For research I read the first chapter of the Gospel of Luke, Gabriel's only canonical Biblical appearance outside of the Book of Daniel. He comes as a herald to announce the births of John the Baptist and Jesus. I also read the section of "Lives of the Patron Saints" describing Gabriel, which discusses his offices in the Roman Catholic tradition.
Lying down that night in bed I had a vision of Gabriel within my imaginal space, He appeared as a man in an ethereal, blueish-gray robe. He had a calm demeanor and his energies were gentle and restrained. I asked for his help with this operation and he twinkled, which I took as a good sign. (NOTE – I saw another twinkle as I typed this.)
Silently meditating later that night, I perceived Gabriel flickering at the edges of my consciousness. It seemed logical that a celestial messenger would manifest quickly and without formal ritual. It occurred to me that since Gabriel had already contacted me, lengthy and elaborate evocatory speeches would be unnecessary during the 30 day effort. I was only mildly surprised to hear Gabriel agree.