
Keep doing this until you are able to hold it in place for several minutes at a time without your hand hurting too much. Come back, and do this exercise again, and try to break your "record". Start with the F chord, either the four-string or the six-string version, and just hold it in place and strum for as long as your fingers can handle. It took me a couple months to get the hang of them (although I had already been practicing the guitar for quite some time by then), and I literally had to just practice them for a few hours a day, over and over and over again. I have one too, and learned barre chords on it. Luckily, you have a stratocastor, which is a fairly low-action guitar (meaning the strings are close to the fretboard). In the long run, you should eventually learn to easily do both, but in the short run, you can pick and choose to give your hands time to build. I'm not one of those guitarists, but again, every guitarist is different. Obviously you'll finger it differently, but that's a start, and for most guitarists, it's actually a bit easier to use that version. If you are looking at your books and see the 6-string version, or your teacher has taught you using that one, try the four-string version by basically doing the same thing you would do in the 6-string version, leaving off the two lowest-pitch strings, with only the four thinnest strings being used. Some people tend to like the four-string version of the F over the six-string version, or vice versa.
