I think you just need to slow down and do some reading. On forums, not every question can be answered in 6 hours. I think there are a lot of holes in your questions and painting with a good outcome is all about taking your time and research. I'll try to provide what little help I can with the lack of specifics.
1) Blow the car off with an air hose, mix mild soap and water in a spray bottle and soak it down, get a squeegee and get as much water off as you can. Next take a rag, put some grease/wax remover on it and wipe 1 panel at a time followed by a clean rag to lift the dirt and help it dry. Move to the next panel with clean rags for those steps. Once you're done, wait for the remover to evaporate off the trunk. Put on plastic gloves, get a tack rag and lightly wipe the spots you will be applying primer to.
2) The mixing ratio for the primer should be on one of the 2 cans (1:1, 2:1, 4:1, and so on). Match it up to the ratio on the measuring cup, fill it to the first line in the first column with primer and up to the matching number in the next column with reducer. Mix thoroughly, pour it through a paper strainer into the gun. All guns are different and have different psi settings, find out what yours is, set it, open the fan to full, and the fluid around 2 turns out. This is just a guesstimate, getting the spray pattern is set by adjusting it while shooting at scrap paper to get an ideal pattern. Once you have it close enough that you feel you can put it down, shoot the trunk with 1 coat, let it dry for around 2 hours to be safe, wetsand it out with 400 on block to get the texture out and have an even surface, then to 600 on block to smooth it. Now you're ready for paint
3) I wouldn't attempt to shoot paint if I wasn't 100% comfortable from shooting a test panel or piece of practice metal. Now is the time when you can really screw yourself over and all the hard work will look like...something you don't want to drive... I suggest you get so far as having the primer ready for paint, since you're in a rush. Then take a day or two researching the paint, your gun, settings, and just general tips. Don't waste your time and efforts up until this point just to screw it up for a sunny day. There will be others, I promise.
4) Get on good terms with your brother and have him guide you through your learning experience.