In a bowl, combine the wet mix with your chicken, ensuring it's fully coated by the marinade. Cover and allow to marinate in the fridge for an absolute minimum of 4 hours, but the longer the better (up to 24hours). Remove at least 30mins before you intend to use it to bring to room temp (important - frying cold chicken causes it to seize up and go chewy).
Meanwhile, combine all of your dry mix. I find this easiest in a small tray, but you can also use a shallow bowl. Dip a piece of your chicken into the mix and fully coat. Really make sure you get the mix in every part of the chicken, this will give you those 'flaky' parts which make the chicken extra crispy. The more craggy/flaky the chicken is the crunchier it'll be. Place on a wire rack and repeat with the remaining chicken.
Heat up enough oil to comfortably cover the depth of your largest piece of chicken. Drop a piece of mixture in, if it slowly sizzles to the top you're good to go. You want the oil to be approx 175C/350F - 180C/356F. The temp will drop when the chicken hits the oil, and that's okay, just try to maintain a heat of around 320F/160C. A medium heat should obtain this.
In batches of 3 (4 max) gently place your chicken in the oil, making sure you add the same cuts at the same time so they cook at an even rate (thighs, drums, wings). Deep fry for 6-8mins on each side or until deep golden and white through the centre (see notes). Don't move the chicken for the first couple of mins, you need the batter to attach to the chicken. Timings will depend on the size of the chicken pieces, how many there are and heat retention, so just be vigilant. Bring heat back to 175C/350F - 180C/356F between each batch.
Place each piece on a wire rack with paper towels underneath when finished and sprinkle with salt to draw out the last bit of moisture and bring out the seasoning. The chicken should be piping hot with the juices running clear. In all circumstances the chicken internal temp 165F/75C (take into consideration it continues cooking slightly once out the oil).