Welcome to the site.
Working by hand with black paint is tough because you can easily inflict the paint with rub marks by using a polish with any abrasives in it. I have seen on here hundreds of times where a new member wants to hand polish his/her black paint and then finds that their polish of choice has left rub marks all over the paint from the abrasives in the polish being rubbed back and forth on the paint.
Having said all that, I would suggest that you first wash the vehicle really well with a quality microfiber or lambs wool wash mitt. Before washing though if you don't have a pressure washer, take it to a coin op car wash and blast all of the dirt out from behind any moldings with the high pressure soap setting and then rinse it off well. This will remove any hidden grit that will definitely be hiding under these trim and molding pieces preventing them from getting into your wash mitt and scratching your paint during the hand washing process.
After the hand washing, I suggest that you use Meguiars Smooth Surface Clay Bar Kit as it is the mildest clay bar that I have found and will not leave any marring if used with plenty of clay lube. Plan on getting an additional bottle of quick detailer so you can go heavy on the clay lube to prevent paint marring which is very easily seen on black paint. If you don't use enough lube and the clay grabs and sticks to the paint, it will leave a mark where it stuck to the paint that will not clay off. Don't panic, polish will remove the mark. If it is durability that you want, the paint must be clayed first or the life of the sealant/wax will be compromised because the sealant/wax will not bond well to contaminates and dirt that whether you see it or feel it or not, it will be there. The baggy test will detect iron particles such as embedded brake dust but it will not detect the imbedded dirt that is definitely there that will prevent maximum durability of the sealant/wax.
Next, using nothing more abrasive that say Meguiars Ultimate Polish or a paint cleansing lotion of your choice hand polish the paint one panel at a time being sure to really work the polish in and not just skimming over the paint with it. I am not saying you will need to push hard with lots of pressure but rather use light pressure and work the polish in overlapping circles giving the polish time to do it's work. Get several applicator pads either microfiber or foam and when they begin to get dirty grab a new one to work with. If you drop the applicator on the ground, pitch it and grab a new one to work with. You may not see the dirt in the applicator after dropping it but working with black paint you should treat a dropped applicator like a hand gun (always assume that it's loaded) always assume that the dropped applicator is loaded with gritty dirt. It's just $2 don't chance it.
After your polishing step be sure that you are working with a quality microfiber towel or the flannel towels bought locally work well if you use one per panel and then retire it for a new one for the next panel. After all this work is done you will be left with an absolutely clean surface that will accept the sealant/wax and ensure maximum bonding.
This is a lot of work so expect that your arm will be hurting. If you get too tired, just finish the panel that you are working on and start the next panel on another day. This would be better than trying to rush through the process. If you do stop and then start on a new panel on another day, go through the washing steps again as driving the vehicle will definitely pick up more dirt. Dirt and grit are the enemy. Keep that in mind and work clean and thorough and you will be rewarded with a fine looking black paint finish and a durable protective coating.
I would suggest a few coats of a quality paint sealant with 12 hours cure time between coats and then a coat of Collinite # 476 Super double coat wax, applied very very thin. This will definitely get you through the winter. Nothing beats Ultima Trim and Tire Guard (UTTG) for durability on tires and rubber/plastic trim unless you want to break the bank for a more permanent coating which you said you didn't want to do. In it's price range nothing works better. If you are treating window seals with UTTG, be sure to run a piece of painter's tape on the glass to prevent getting UTTG on the glass because if left to cure on the glass it is a bear to get back off the glass. Polish will remove it from the glass but it will also remove it from the trim so just do it right the first time as tape will be required either way.
I hope this has been helpful, TD