Can any of these products be used by hand or is a machine required?
Answer is yes, you can with hand.
The advantage of a machine is that it does several hand strokes per second, so you can do more car in less time with more consistent results and much less effort.
You can polish a car by hand, but unless it’s a small patch, no one ever does.
There are youtube guides for hand polishing though.
There are four brilliant products to use with no machine:
1 - Autoglym Paint Renovator.
If I could only have one detailing product, it would be this. It’s great for hand cutting out paint defects marks, grease, stubborn tar spots. It can polish out scratches. It’s a fantastic product.
2. Autoglym Super Resin Polish.
For a close to polished look without the hand scrubbing. It’s mildly abrasive but also a filler, which is the way to go by hand.
3. You can use a sealant then on top. Gyeon wetcoat is best in class for effort / reward, very good gloss and protection.
4. Autoglym - Extra Gloss Protection
You might not want to get your car wet straight away, so you can use this on top of the super resin polish. Use wetcoat for maintenance washes.
I’m not an autoglym fanboy... I use lots of products, but these four will be perfect without a machine to apply.
For machine polishing:
You don’t need a rupes to get started. There are some more hobby friendly options for machine polishing.
I’m might lose some street cred for this next bit.
If you want lowest cost least effort best results:
1- Paint Renovator for eye catching defects
2- Demon shine - use wet or dry.
I know people turn their nose up demon shine, but price to effect ratio, it’s unbeatable.
I have all the gyeon stuff, but still keep that on my shelf.