Get Help from Gnostic Instructors

1. The instructor on Gnostic radio taught that pranayamas should be done in the following manner. Mentally pronounce HAM, while inhaling through the nostrils, hold for as long as is comfortable, then exhale in a brief way. Of course imagination is important in this, and more can be said about it, however my question is this: Does one continue pronouncing the mantra HAM while holding? I've done a lot of reading over the years and I am confused to as if one ceases utilizing the mantra during the middle part where the energy is being held in the chalice of the brain. Is it just silence, and visualization at that point? He says to imagine a white light that is filling your mind and healing you, is it OK to envision Christ is the center of that image? I've found it was helpful and gave me a lot of willpower.

2. The same instructor has said in other lectures, in particular I'm thinking of one of the spiritual defense lectures, or Christ Mantra Mind Protection, or one of the other couple of mantra lectures, that one should continue to use a mantra 24/7 and not switch mantras. I mostly abide by this but obviously there are at least three times a day when my practices will conflict with this: Ham Sah pranayama, when I'm eating and using the mantra KRIM, and when I wake up in the morning and am trying to remember my dreams (RAOM GAOM). This excludes conjurations of course. Is it OK to use these mantras at that time, then switch back to my original mantra for the rest of the day?

3. Are seeded grapes a decent way to get the air tattva?

Thank you.