I have also done it. Works pretty well. I wouldn't do it on a really nice gun (take it to be professionally done), but if the gun is a daily user or a less expensive one, the do it yourself kits are great.
If it has any collector value at all, re-bluing will ruin it. An OLD blue gun should look brown. Bluing is actually a rust process.
I have never tried the home kits. I did some actual bluing and nickeling years ago. The finish only came out as good as the prep work. Everything had to be polished to a mirror finish and free of any grease or oil.
It's a Winchester Ranger model 140 semi auto 12 gauge. I dont think it has any real collector value. So you can polish it to a bright blue? The ones I seen were flat. But those were the kit flint locks. What would a good brand of bluing?
I have done a couple of guns too and has worked nicely. X100 on the prepwork i used progessively finer steel wool on the cleaned metal and then applied the bluing. i would try not to pool up the gel unevenly it will leave spots. eveness is the key.
If you want the flat look you can do it that way too. My father in law didn't dry out his muzzle loader and it sorta rusted in the case. He pulled it all apart and had a place glass bead it with fine stuff and then he blued it. Looked awesome and didn't shine anymore. I'm thinking about doing it to my muzzle loader.