My experience, based on having tinted about ten cars and a couple of houses...
Expect to make a mess of the first couple of car windows you do. Based on the quality of your builds, reflected in the pages of this forum, the first couple will not match the quality of the car.
Basically, when I first start tinting again after not having done them in a long time, the tinted windows will look like crap... bubbles, pollen & dust, hair, fingerprints, etc. After I get mad and pull the film off and redo them a couple of times, then they start to look much better.
Unfortunately, I don't have a garage at this point, so I have to time installation around warm weather. I also always end up with trash under the glass... dust and pollen mostly. Even when I get in the car and close the door while tinting, the doors have been open long enough to let dust and pollen settle on the door/glass while i'm getting in and out of the car, cutting film, etc.
I did the Testarossa a few weeks ago, during a warm spell. I didn't do a pro job, but it's good enough for now. The dust is more noticeable from inside the car, than from outside. Once I get the headlights replaced and minor bodywork done, I plan to have the paint freshened up, then I'll have a professional tint job, or at least re-do the tint myself. I went with limo tint on the rear glass and on the factory "blue" strip at the top of the windshield, and Georgia-legal 35% on the doors. When I redo, I may try putting 20% on the doors.
Since it is not a daily driver, I wasn't overly concerned about heat reduction. Primarily, I wanted privacy... before I purchased, I didn't think about how many people would be pointing, taking photos, and staring at the car. Frankly, I still find all the attention a little unnerving. At least now, with darkened glass, I feel I have a little more privacy.
My suggestions...
1 - watch a couple of YouTube DIY Tinting tutorials
2 - take your time... Patience, Grasshopper!
3 - park the car inside a clean garage, then close the door and wait for a while so dust in the air has time to settle, wet the garage floor slightly to trap settled dust, then clean the windows (inside & out), door cards, window framing, and weatherstripping around the windows
4 - have the right tools... razor knife, squeegee, scraper, heat gun, steel ruler, water spray bottle, etc and quality film
5 - follow the directions supplied with your film when cutting out and shaping the template... for curved glass, use thin strip film or heat gun to shrink the film, similar to shrinking vinyl wrap for curves
6 - wet your fingertips to avoid leaving prints and crud in between the glass and film
7 - pull the door card away from the door or even remove if possible... not having to fight the inner door wipe makes it easier to clean the glass down into the door, and to prevent trash getting inside the film
8 - steel ruler is great with the razor knife for minor touch-up cuts
9 - take your time

10 - leave the window rolled up for a few days while the water between glass and film evaporates
I hope the suggestions help. Based on the quality of your work, I have no doubt you will be able to do a great job on window tinting as well... after a few practice runs.

lol