Hi Ronny- Welcome
I will offer suggestions or tried methods that work for me and as others have already mentioned theirs, you may get some other great suggestions also.
1. yes, with practice you can paint trim without taping. When I learned years ago, I had a practice wall set up and my mentor used to make me practice , practice, practice on wall/ceiling trim as well as window trims. There are some post in the archives that talks about painting trim. I find not loading your brush heavily also helps a great deal and I like using a 2 1/2 to 3" brush for wall/ceiling(angular)-, starting in the corner and fanning the bristles out as I go and the outermost edge of the bristles ride along the edge line of the ceiling/wall. Also not to have a build up of paint on the bottom edge as this could lead to hatbanding,flashing when you begin your regular painting. I am also a decorative painter, so in my case - delicate blue painter's tape- 3m # 2080 is my "best" friend. Found with an orange core/blue center or yellow/blue center. Tape lines are clean as a whistle and NO paint seepage.
2. Primers ARE NOT necessary for every job. You really need to examine each person's substrate thoroughly to determine if a primer is needed. May need to ask homeowner some questions also (if they know). There are lots of variables to determine if a primer is needed or not, how long the wall has been before painting, what color is on there now, what finish is on the wall, oil/latex, as you mentioned, dark colors going to light, painting reds or transparent colors, dirty walls grease, etc., mold/mildew, tinted primers close to the final color choice; so you see , there are lots of things to determine whether primers are needed . just do a thorough examination; if there are any doubts, yes IMO you should prime. Primers are indeed a person's best friend, but they are not always needed , and oh two coats a selected paint .
3. 3m makes a masking system you can use; use a taping knife and press down and push against the carpet, clean the knife if paint gets on it, also don't use a loaded brush, that would be your enemy.
4. Corona brushes- 2, 2 1/2, 3" sizes, champagne nylon vegas or vista, chinex-excalibur.
www.coronabrushes.com5. buckets/grids, but I also use trays if I am doing only one room.
6. 3/8ths purdy dralon white dove most of the time (smooth walls)- also wooster's
7. Best paints - are to me a personal choice. Some like other brands better while others like something else. I use lots of different paint brands . I do use a lot of Ben Moore, but there are lots of great paints out here; ppg-manor hall, p/l- accolade, SW- Valspar-signature series, etc.
Primers & their products- my ulimate choice is XIM all the way, but I do use a lot of BM-fresh start and SW- preprite, Zinsser's. Oh, and I do interior repaints- not new builds.
good luck