Pretty much summed up there.....keep different mfg seperate as they do vary considerably in weight....extra weight means less powder capacity....less capacity with the same powder charge means higher pressures, so be careful.
I seperate and weigh all my cases according to weight after trimming to length, primer pocket uniformed, flash hole uniformed, case neck chamfered inside and out.
As for make. I personally really like RP...Remington Peters, Very consistant weight from case to case.....consistant weight means consistant loads with small standard of deviation...translated means good consistant accuracy if you do your part.
Get a good loading manual from any of the mfg's and READ IT thoroughly, and understand why you are doing what you are doing. If you are unsure, have someone with experience help you out.
Last thought about loading. Do it when you can give it your UNDIVIDED attention, dont watch TV, etc etc. Hell I don't even have a radio on ,so I concentrate on the job at hand. Loading is fun and safe if you follow the rules.