"I have a glass bowl, and one day I will try that experiment."
It's probably best to work up to that. Start by building a skill with an uncovered psi wheel. With practice, you'll start to get a feel for the mental states that facilitate smooth movement, and those that don't. For instance, being preoccupied or frustrated seems to invite failure. But feeling content, clear-headed, and focused on nothing brings success.
In magic, Anton LaVey described a ritual chamber as an "intellectual decompression chamber" - a place to feel and not to think. Thinking is the barrier to success. I take the view that magical rituals and psi techniques are one and the same, beneath the trappings. They are ways to get the rationalising mind out of the way, making room for the magic to occur.