I've used a ton of different brands of coco and used to avoid the chunky stuff, flushed the fuck out of it until the water ran clear, etc. and came to realise I was fucking myself over in the long run. Chunkier stuff made it so I needed less perlite, flushing it out so much removed the buffer and using finer grades of coco just lead to the pots getting clogged. I never bothered with the stuff with added nutrients though because I always wanted to be in control of them.
Back in the day I experimented with the ratio of coco to perlite going in 10% increments and found that 70% perlite and 30% coco to be the best ratio with the rate of growth, yield, etc. but it was a cunt to keep up with the watering since I was doing it by hand. In the end I settled on the opposite, 70% coco to 30% perlite, because it retained the water much longer and gave better results than going less perlite. That said since then I've gone 100% coco without issue especially when using the chunkier stuff from bunnings.
The best advice I could give would be to mostly expand the block with boiling water from a kettle or stove. Gnats are an absolute cunt and you'll get them without fail if you use cold water. The second best advice I can give is to gradually saturate the coco so that you have a very shallow pool of water beneath it to work with. 1cm-2cm is all you need and I would do so with 1/4 strength nutes with a bit of calmag added to it as well. The reason is that the coco will have it's own pH and it will absorb nutrients as well so if you give it a wee feed and give it time to equalize itself you can get an accurate reading of the pH and alter it as needed.
One of the biggest things things I learned along the way is that the coco will become acidic over time especially at the bottom of the pots. If you test the run off the pH can get super low and flushing will seemingly take forever to fix it even in a shower. You can counter this by giving it a watering with a super high pH and then flushing like normal or if you want to take a lazier option you can just increase the pH of your feeds to compensate as time goes on which is what I would actually recommend until major issues arise because you will have nutrients far more available at different pH ranges. The way I figured that out was thinking if I start at 5.8-6.2 and the pH changes I'm instantly moving away from that ideal but if I know for a fact the pH is going to drop and I start high it will move towards that ideal range and below it unlocking nutrients to their full potential as it goes. You can choose to lock nutrients out or unlock them, either way the pH is going to change and giving the pots a proper flush is an inevitability.