You don’t have to use candles in evocation, it happens to be popular for varous reasons. Cups of water are fine, and there’s a couple sources I’ve read where spirits, especially angels, are fine with plain and simple things like water, and sometimes nothing at all, which is sometimes my experience as well. Their sigil by itself is fine. Water, candles, etc are mostly for you, the magician, to channel energy, but some entities have color and other associations you use candles or other things for.
You can layer petitions, I find there’s greater control involved with layered petitions than one generic petition.
Planetary Magick by Demming & Philips
Grimoire of Armadel
Complete Magician’s Tables
Demons and Demonolatry Dot Com (use their search bar for a specific entity, they cite multiple grimoires for demonic correspondences such as dates, hours, elements, etc).
If you are asking “how do these authors come up with this stuff?” then it’s a combination of intuition and spirit work, such as asking nicely. Conolly cites that she references the Dukante grimoire, which is kept private in the family and has never been published. The information I have personally is a combination of reading various sources and deciding what works best for me and my practice, as well as what is in my culture. There’s a lot of wild stuff out there that I just flat out don’t believe but mind my own business, including some things even well known authors write (fame and renown don’t mean accurate or good).
I wrote this post for people still learning how to intuit and research on their own, hopefully it can be helpful to you in some way: