To square the frames, you need to remove the trim boards around the frame. Be careful removing them so they don't have to be replaced. Once they are removed, you should see the shims and blocks used to square the frame originally. The rough openings are always cut bigger, so there will always be some shimming involved.
The product most locksmiths use is any type of silicone spray. Don't Use WD40, it contains a substantial amount of oil (petroleum distilates) that tend to collect a good amount of dirt and dust. In cold weather, the oil in this product can and will get tacky and over time will start to solidify causing the lock to fail.
Q: I am attempting to put an internal window into a currently load bearing wall... any advice on how to do it? I am thinking about building a frame out of 2x4's but I don't know if that will support the load... any help please.