Currently so close to A+, it's killing me. I have been an A- for 2 whole months, so when I got to A I was determined to keep it and then go higher. So close I tell you, but when I lose a lot, I take a break and switch up weapons. My idea is that sticking to a single weapon will help you learn it inside and out, but should you come across a counter to that weapon, you may as well be splat fodder. So I use a bunch of weapons, so I never find myself in that situation.
AAAAAHHHH DON"T GIVE UP!!!!!!!!
I know full well the struggle from A- to S, (I had dropped from A+ to A- 4 times, and from A+ to B+ twice. A+ 90's, not low A+) and how BULLSHIT the matchup can be. Looking back on it now, I know the sole reason it's so hard to progress at all in these ranks, for both me and everyone else. It's simple: we're not good enough (was in my case). A rank is the trainer rank, as I like to call it, for S. It sounds douchey of me to say you're not good enough, but let me explain a little. I don't mean it like you think.
(Although after writing this whole thing I realized I didn't explain it until the end, so please forgive my jumbled ADD thoughts. I'm actually really smart, I promise.)
Before making it to S rank, A+ was the hardest, most ridiculous rank to ever progress in. Now, since becoming an S rank player, the couple times I've dropped back down to A+, those matches have become cakewalks.
Right now you just need to keep plowing through with your best weapon. You might think that you might have reached a point where there's not much left to learn about your main weapon, and know every good method with it- I assure you that you don't. I main almost exclusively the two Luna Blasters (normal and Neo), and yet I still find new methods and tricks that help me significantly (and let's not talk about the times I find other Lunas whose play style completely destroy me). It's best to keep chugging with your best, and train up with other weapons in turf wars. Now it's true that you can't always use the same gun for every set up (i.e. I use the Hero Shot Replica on Moray Towers, my strategy with the Luna doesn't work there yet), but I've found that many maps that seem disadvantageous for my weapon actually have viable strategies that I just hadn't found before (like going in from behind at Kelp Dome, etc.)
The same applies to the counters to your weapons you may come across. Now, I'm definitely not saying that you'll be able to overcome any and all counters while playing that particular session, but think about what was happening after the match is over. Could you have taken a different route? Was the enemy focused on a certain area that you could come in from a blindspot? Is it better to just avoid the enemy until he moves into a better position? You might be able to think of something that you can try the next time you're in that situation. This worked for me in Bluefin Depot; I used to always get destroyed by E-Liters on the other side of the map. I've learned (since I'm good at dodging their shots when I'm moving) that I can zig-zag up close until the retreat inward, and then wait until they pop out on the side exit of the platform (most likely in an attempt to snipe me while I climb up the wall. By staying to close to the side path they appear on, I can splat them with no problems, consequently countering their counter (not that it works every time, as nothing does in these kinds of games). Observing enemy movements is key for these kinds of strategies, so if you've ever noticed how most .96 Gals like to throw out Splash Walls in certain spaces, or how Rollers like to hide on top of the boxes at Walleye Warehouse, you can start formulating plans for future matches.
Also, when I said you weren't good enough yet to make the rank, please don't take it the wrong way. I'm completely on your side. It's not like I'm saying it'll take months to "git gud;" I mean it in the sense that the A-, A, and A+ ranks are really good at training players to think differently and more openly about their play style, as well as help them figure out for themselves some good strategies to use on certain maps. I'm basing all of these assumptions off of my own experiences as well, so they may not work as well for you as they did for me. Even if it's unhelpful, I hope you gain something good out of it.
And if you're wondering where I'm at in my rank to be talking like I know everything, here's my info:
In-game name: Isan
Level: 43
Rank: S (60-something)
Effective Weapons: Luna Blasters (absolute best), Sloshers, Hero Shot Replica (just a cooler looking Splat Charger), and to a small extent on certain maps, the Heavy Splatling (not the Deco).