Brake Squealing Problem on 98' Silverado

[Ateam311]

Been awhile since I've posted here, but howdy everyone!

Anyway, about two weeks after getting new brake pads installed (we had someone else do them this time as opposed to doing it ourselves), I noticed that the brakes were squealing like crazy. So, my father and I pulled the front tires off, sanded down the pads a bit, and threw the tires back on. After going for another drive, I noticed that our effort was wasted.

A few days later, we proceeded on over to the Advanced store and talked with a guy over there. He told us that the guy who installed them probably didn't put any lubrication on the bolts or on the back of the pads. We ended up buying a $6 bottle of lube, pulling the tires off again, and putting lube on the two bolts that you have to take out in order to switch pads and on the backs of the pads. Afterward, I went for a long drive and didn't hear so much as a peep from the front brakes.

Then about a week later (just a few days ago), I spent a good two hours washing the truck down. Afterward, I took er' for a ride and heard very faint squealing from both the left and right-front brakes. I didn't think much of it at the time, but then the next day... I ended up driving through a pretty bad rain storm and noticed that the brakes were as loud and obnoxious as they were before we put lube on them.

So what did we do wrong? Did we use bad lube, or did simply we not let the lube sit long enough before putting the pads on?

Thanks in advance!