Honest Kitchen, usually I really enjoy your longer posts - they are informative and useful. This one, though, is full of slightly off advice - some harmless, some really not so.
For starters, that booster seat has not been crash tested either, and is a pretty unsafe place for a dog to be. On the front seat in a car with airbags is a deadly spot for a small dog. They will be MUCH safer in a crash tested harness, or a crate strapped down well in the back seat.
A nice crash tested crate can double as a carrier. You won't save money, though, good crates cost a goodly pile of money. I'm not talking about aluminium wire crates - these are a very unsafe choice. Fabric crates are safer than those, but still not great (and likely to fail if you strap them down well enough). You do get solid, tested plastic crates, though. And then there's this beast:
Variocage dog crates, Variogate dog gate, Safety net partitions, Universal net partitions and accessories. Variocage hundburar, Variogate hundgrind, MIMsafe säkerhetsnät och tillbehör för säker transport av hund
There is definitely a case to be made for the correctly sized brush. But have you ever watched your local master groomer? Those teeny tiny little dog brushes are not on their shelf. Medium sized is typically the thing for the itty bitty guys (and, typically the thing for the big guys too). Good brushing technique is what will make the biggest impact. Using smaller brushes can make grooming take very long, and can increase your pets discomfort which in turn makes grooming harder to get done over all. Mostly harmless advice, this one, though.
The advice to use human nail clippers not so much. Human nail clippers are rarely sharp enough to make a nice, neat, clean clip. They compress the nail as they clip - fine for a thin, flat nail like our human ones, not so fine for a round nail. Dogs nails clipped with human clippers (or blunt clippers) tend to feather and little bits shear off. Very uncomfortable. A set of small nail shears, with a blade that you can sharpen, is a much better bet.
With one exception - if you have access to human nail industry nail clippers, and keep them VERY sharp, you're probably fine. That silver thing you buy over the counter at Boots not so much.
Please do thank Maggie, the author, for her efforts in writing so many of these articles, but in this case, especially about the booster seat and the nail clippers ... not good advice in general, not if safety is your aim.