I don't know too much about blasters, but I'll tell you all I know!
-Get into a rhythm of Swim > Jump > Shoot (then repeat over and over). Not only is this the fastest and most ink - efficient way to move with a blaster, it also makes you a harder target, as opposed to just standing still or walking forward while firing.
-In a close-quarters stituation, you have 3 options:
1) Swim/run away - this is when you're seriously damaged with no chance of winning a fight.
2) Jump around and shoot - only use this in very close quarters situations, because it will make you a harder target, and it's almost impossible not to get a direct hit at this range.
3) Just stand still and shoot - this is useful a little bit farther away from your opponent, especially if they have already damaged you a little bit, but you're not right up in their face. Not jumping means you are more accurate, which means you can get a direct hit, which means you can come out of a bad situation on top.
You need to abuse the fact that blaster shots explode, meaning that you can kill people in 2-3 hits, depending on how far away they are.
Also learn to predict your opponent's movement. This means that if you hit someone with an indirect, you can predict where they'll go and then kill them with another indirect.
In terms of gear, I'd recommend abilities that make you more ink-efficient (main saver, sub saver, and especially ink recovery up), because this thing is veeeeery ink-hungry.
Swim speed is useful for the Swim > Jump > Shoot strategy, and a little run speed never hurt anyone.
Besides that, it's really up to personal preference.
I'd recommend using a high sensitivity for motion controls with the blaster, as it means you can turn around quickly and splat people sneaking up on you.
Good choice picking up the blaster. It has a fairly steep/high learning curve, so don't be worried when things go badly in the first few games. To practise, use it in Turf war first, and then when you feel you're ready, go to ranked (this is where most of the improvement happens).
I think that's all I know about the blasters, but if you have any questions/don't understand anything, feel free to ask me or any of the other lovely people on Squidboards!