couple rules with wet sanding. First, only use 3M wet/dry paper, avaliable in sheets, cut each sheet in half, and fold that in thirds.
Second, Always use a block of some kind, never just your hand. a nice soft block will prevent "finger marks" and hug contours well. the idea here is evenly distributed pressure. block with contours, and change up directions often.
Feather damaged paint with 220/320, but to be ready for paint, go over that with 600. ensure that all 320 block marks are gone, replaced with 600. hope that makes sense. for chips on hood/bumper, fill them with a one-part nitrocellulose spot putty before your sanding. no need to feather that stuff. remember to properly feather paint, there should be at leat 1/2" of each layer visible in a concentric fashion. Dont be "diggin ditches" in the paint. they WILL show up in the final result, lookin like dents everywhere.
For all spots where the paint is currantly in good shape, I reccomend a scuffing gel, combined with red or grey scotchbrite. most paint companies sell some type of scuffing compound, its kind of like pumice soap. has a nice even 600/800 grit to it with grey pad. 320 grit when used with red pad. also, it doesnt leave block marks. if you cant find some, I'll be glad to help you get some.
That said, If I was you, looking to get the job done quickly, with the least amount of effort, I would do things a bit differently. get some tools.
finish DA sander, not a big body DA, a painters DA, about 150-250$$
painters backup pad, 6" about $10
2 boxes of 320, and go to town. the painters DA will keep the swirl small, so you can paint over the 320 scratch, and the painters pad is thick and soft, itll keep you from diggin ditches. get some 1500 grit as well, itll be used on the same da to colorsand the clear later.
This method requires some type of air compressor, but will save hours and hours of back breaking labor. you ever tried to wetsand a rocker? if you want professional results, you need professional methods/tools. its not a huge investment, but its up to you. I do this for a living, and I only wetsand in certain circumstances, like if I'm gonna shoot gold, or silver over primer, and I'm not gonna use any sealer, then I wetsand with 600/800. You should most definetly use a sealer as the first coat of paint in the final "paintjob".
couple other things. get some good self etching primer to cover bare metal and any filler you use ASAP. and oh yeah, take out the quarter windows. I know you dont want to, but I really wanna see you succeed. you seem determined enough to do the job, just dont rush into prep without the funds to paint it soon. prep work isnt meant to sit around. for any paint to adhere chemically, it should be painted within 8 hours of the last scuff, on any given panel. more on that later if you want. good luck, and get your ducks all in a row before starting the prep.
94 V8 on 17" custom paint, R.I.P
97 Mark VIII LSC yeah
08 Ford Edge, white for now