Google? what's a google?
Seriously though, since you put the effort to make the guide I'll try and help a bit.
http://www.irfanview.com/ has a batch conversion which will make sure all pics are the proper file type, as well as a renaming and resizing in the same function. You can do it all in one shot with a single program. I find it more useful than other 3rd party programs, as well as more reliable. If you open a pic in it that was renamed but not properly converted it will tell you and change it accordingly.
I'm a Firefox newb, so I appreciate all the advice there...I got fed up with IE for various reasons.
Software for double pics is extremely unreliable, I agree with you that nothing compares to your own scrutiny.
Resizing pics, I only try to upsize if they are under 450 (pixels) in height, using irfanview. If they become too 'dirty' (idk how to word it,) I just delete them. I only downsize when big to the point of jagged lines on my PC.
For traits and descriptions in my girlsx files, I aim for popular fansites and wiki, but it can be hard at times so I just try what I can see and read. For traits, if you can't find much posted info, pics can give you a lot of info to go by when making the pack. I would suggest making the pic file first unless you know/follow the series/game.
In my experience Mediafire is the most reliable free file sharing source. Problems seem to arise due to the name of the file. I don't know how to explain it well, but using well known names can get your file blocked. Explaining it properly here and purposely misspelling it or randomly naming it seems to work. Just make sure the extracted files are named to your preference.
http://lu.scio.us/ Doesn't seem reliable anymore. I could very well be wrong, but from my understanding they changed sponsor. Obvious under 18 characters were immediately removed from the site. I'm not a huge loli fan, so no prob to me. But...apparently any character DRAWN who is, or believed to be under 18 y/o is subject to being removed if found out by the sponsor. When it comes to hentai I've never considered age of the character in the series to be THAT important, but it seems to be increasingly valid in NA and EU which will inevetably be a decrease in the availability of art.