Newb question: do I need water to buff?

Brush? I'm not he most experienced polisher in the world, but I've had many opportunities to critique the field. First detailer I ever met worked as the detailer in a car dealership. That guy was an artist, and I've never seen his equal in 48 years. What I have seen is every kind of amateur chemist on the docks that mixes their own "superior" products together from different manufacturers while uttering some hocus-pocus. Rcrapps is right-on, follow the manufacturer's instructions, and, stay with one manufacturer. The manufacturers refer to their products as a "System" quite often for a reasom. There's no point in spitting in the eye of a Chemist's education.
There are quite a few important aspects to applying product during the buffing process.
Use a dedicated buffing pad for each product. Clearly mark every buff pad and product container so they don't get mixed up or cross-contaminated. If you use a pad with a coarse cut and then switch to a product with a fine cut on the same pad, you're still buffing coarse. Always start with the finest cut that will do the job; you're removing gel-coat or paint at every step.
Detail Harold always dispensed product from a condiment style squeeze bottle, and you'll notice that smaller bottles from manufacturers dispense from a small hole snap-cap, and the gallon bottles don't.
As for how to avoid burning and abrading through finish, that kind of thing is best learned by first-hand instruction. Same goes for identifying what you are working on. You should probably never try to buff a clear coat. If you know nothing and are just starting to self-educate, practice on a friend's car
By the way, the concept of pouring product into a container and applying it with a brush, if that is what you meant, is wasteful. That stuff isn't cheap. Water is for washing when you're done. If you've accumulated dehydrated product in a container and need to thin it, use the manufacturer's recommendation. If they don't provide it, read the product MSDS. A MSDS is good reading, anyway. You'll be surprised what deep-dark secrets are hidden in them.
The only brush you need when detailing, is one of these.

Meguir's stuff is crap. See if you can get Presto compound and Presto makes an excellent synthetic wax...... if not, get Aqua Buff compound and follow with rejex.......but if it's cold, no wax, synthetic or natural is crap. No, you don't need water to buff, but BEST if you rinse the boat off after compounding and before waxing.

I am a big fan of the sea-shield system. Their website has lots of information and you can call them to get more advice.

I now use Carpro products and find the results more long lasting. I buff with sea-shield heavy cut or cut and polish, or 3m imperial compound if it's I rough shape.

I finish with carpro essence as the final buffing product. After my first year on my 88 Ocean, I need only use the Essence. I just started today.

For"wax" I use quartz. It's easy to apply, but takes a bit of practice. It's not cheap, but nothing lasts longer, nor cleans easier. It doesn't take quite a bit the first time you use it, but less each successive year.

Hi,

When you have no water available: before polishing, wipe the polished area for example "Bilt Hamber Cleanser-Fluid", use a spray bottle and microfiber cloth to get rid of scratch-resistant dust. When the surface area is much more advisable to use one step compouding material, cutting lamb's wool pad, and I have achieved a great after-Rupes Big 21 foot machine. Wipe the compouding off with microfiber cloth and Bilt Hamber Cleanser fluid before pre wax. Work on a small area at a time for example 2 'x 2' (feet) when compouding. Narrow the area with tape and be systematic...

One step compouds video


And you one step compoud instruction
https://www.autogeek.net/boat-cleaner-wax.html
NBs