Lighting
Get a Scangrip with a diffuser light cap, or a comparable high quality detailing light. The diffuser will help you point out deep scratches in an area of smaller scratches. When evaluating paint with your Scangrip, remove other external light, to give yourself a more accurate picture of the vehicle condition.
Clay
One more pass with clay bar even when you think it is done. Sometimes you miss some bonded contamination, even when it seems like you removed all of it from the previous effort.
Backing Plate
First time using a DA polisher. Mark your backing plate with a sharpie. Just a straight line down the side, which allows you to always see if the backing plate is spinning freely during the polishing step. Credit to Mike Phillips on this one and being mindful in this situation is a key to self-teaching.
Polishing Oils
One more application of panel prep after polishing. Like using a clay bar on a section one more time, that second spritz of panel prep over a vehicle is that insurance step to remove all of the polishing lubricants. I personally recommend that panel prep be an actual panel prep product, not just an IPA homemade mix.
Humidity
Remember humidity is moisture. Humidity affects sealant and especially coatings, but it also makes polishing and removal of polishing lubricants trickier. Be mindful of the humidity in the air and tweak your processes accordingly.
Quality
Don’t be cheap particularly with the wrong products. A polisher and absolutely a premium polisher can make a difference. But also, high quality level and sufficient number of polishing pads that are also compatible with your polisher help tremendously. Having an ample amount of microfiber towels from a reputable premium brand supplier also is in your best interest (i.e.Autofiber & The Rag Company). Even when people invest in a flashy product like a polisher, not addressing the other resources is a common reason why people go backwards trying to improve the appearance of their car.
In Conclusion
If you want results out of your detailing to look amazing or get that prideful feeling inside, don’t just go through the motions. That does not mean getting the trendiest, most expensive item, or most advanced products. What I am getting at is detailing is effort throughout duration. The intention in the materials, understanding what and why, the gentleness and patience in your techniques, will yield an appropriate result. If you order some miracle product off the internet people rave about allegedly and do not put the same energy into everything else, you will be disappointed. One of my favorite things about detailing is that you get what you put into it. I see the sweat, exhaustion, and mental fatigue, in the beauty of each car I detail.