In reply to Matrix:
Strength is very important for climbing but nevertheless it is not the only thing. Technique and the mental aspects are equally if not more important than strength. If you can boulder at V3 then you already possess enough strength to climb well above 6a and 6b. No 6c will have anything harder than V3 and neither will most 7as or even 7bs If strength is not your limiting factor then getting stronger may not improve your lead grade at all, or at least will have only limited results.
More than anything you probably need to climb more, improve technique and the mental aspects of climbing.
Learning to climb on slopers is a very specific skill and strength. Its essential for some kinds of climbing, like gritstone bouldering but almost useless for others like limestone sport climbing. The strength needed to hang on slopers is different because your fingers are in a different position and isometric training provides little benefit outside of the joint angle trained. However when it comes to climbing on slopers, as opposed to just hanging on them, then there's a lot of specific technique required too. Body position and body tension are very important for climbing on slopers and the best way to learn these techniques is by climbing on slopers.
If you can climb more regularly then do that and limit the amount of strength training you do for the moment. If you can only train at home then think about building a board to train on if you can. If that's not possible either then for general home training its probably best to concentrate on general conditioning and core strength and of course a fingerboard. Campus boards and sloper training seem too specialised for the grade you are climbing at the moment.
Finally for any type of strength training to be effective you need to make it progressive. You need to be modifying the exercises you do each week by making them harder as you get stronger: adding reps or weight or modifying the exercise.
