There are some other ways to win besides spamming the pins you are good with it just depends on where you are in the game. If you are just starting out then using the Slashing pins from Jupiter of the Monkey will be a godsend as well as Natural puppy bullet pins, a healing pin and then a couple of high damage hard to use pins for those special instances (The lazy bomber is especially good for this). Some tricks are to get fusion star boosting items on your partners and just spam there fusions either as damage dealers or a quick heal when necessary (Beat's level two fusion at the start of the battle is a godsend for killing those annoying pigs and high health enemies). Another good beginner strategy is to ignore the top screen but still try to get used to doing two things at once. The later bosses rape you if you can't do well with looking at both screens. Minamimoto and Konishi are impossible without it.
For the more advanced players you have more options left open for you. One of my favorite strategies is to get all SOS increasing items and then equip the pin the starts you off in SOS at the beginning of the battle. You can end up doing easily over 1k damage with regular pins and attacks simply because of all the stat boosting items you have one (some of the best in the game) but you can't get hit which is hard. That is for more advanced users and for regular enemies not bosses they will cream you unless you can avoid damage and hit them frequently
For farming what I do is the level two fusion as well as a healing pin, the Wolf (lets you dash and attack at the same time) pin and the brainy cat/lefty cat/righty cat trio. Granted with this you'll only have one attacking pin probably but you will also have a faster booting pin, more damage and also a quick way to kill things. Farming dark matter from Beat makes this strategy shine.
Personally, my choice line up is Kanesada (Evolved slashing pin from Jupiter of the Monkey) pin with the Wolf pin, Lightning Rage from Tigre Punks, Pig pin to increase my drop rate, a pin that boosts pin uses and Healing Whale form sheep heavenly. It really is whatever works for you though because the game has so many options to what you want to battle with. My friend just has Anguis (999 attack one shot) and Beat's level two fusion at the start of a battle and can usually finish the battle in the first 30 seconds but it's personal so don't take advice and just play around till you get something that works.