I really enjoyed the splatling when it released, and made it one of my four standard loadouts. I can give you some starting tips, but you gotta see how you wield it, and modify it to your play style.
although the splatling works like a charger, it serves to suppress and contain. you still need to hit about four times to splat someone. an opponent can still escape if they're fast enough. when at a distance, paint both in front of and behind your target to cover their escape points, then aim for a direct shot.
if it's close range and you're ambushed, charge your shot enough to shoot a little, and aim directly at them. (that's not to say a full charge won't do the job, but if they're too close, a tiny charge should do, and give you mobility.) if it's one against two+, focus on keeping them where they are, or make them retreat until your team comes. if you're fast enough, you should be able to handle two.
use your sub effectively. the splash wall has cut off entry ways and blocked incoming fire countless times for me. the splatlng offers just enough ink to throw a wall and shoot a full charge without refilling. just make sure you can retreat, otherwise you'll be standing there with no ink.
take your time, and evaluate maps and pathways. I guess you'd already know this since you mained the Eliter, but since the splatling has less range and damage per shot, you'll often be on the edge, or in the middle, of a scuffle, and squids like to sneak up on splatlings. like I said earlier, always have an exit (but that's with any strategy, so you should be good).
for gear, it's nice to equip an ink saver main, and at least one damage up buff (whether it be three subs, or a main), so you can continuously shoot if in a bind, and keep your damage output from afar. I also use a defense up, just in case I can't escape, and need to squirt a tiny charge to splat someone while they're hitting me.
hope this helps! If anyone else has other strategies, chime in! I'm curious to see other techniques too.
