Miracle grow spray attachment query

As my soil is so poor I was considering buying a miracle grow hose attachment feeder spray thingy (technical term)
Is it worth it? Does it work? Is it idiot proof and easy to use? I'd be grateful for all thoughts and advice. I'm feeling pretty confident somebody on here has experience of said contraption.

 

To inprove you soil you would be better off digging in some organic matter, compost, manure, worm cast etc.
The miracle grow uugimaflip, are good for applying feed, and are straight forward but RTFM (read the flipping manual).

 

@Cuttings glad to see I'm not the only one who uses technical terms like they're meant to be used. I'm going to put a layer of garden centre manure over the borders and tease it in when summer ends but I was hoping to give my plants a boost now to compensate for poor soil. They could do with a snack, ooooh somebody said snack.....
I'm a bit nervous of spraying anything direct onto flowers and foliage but it must be OK as it seems a popular thing to do. Now where's that snack.....

 

@Cuttings or anybody who might know please. Ive just used the feeder with the 200gm free sachet of food. I could see bubbles moving through the feeder so assume it was doing what it was supposed to do. However after watering my borders for quite a considerable time the water in the feeder was still very blue. Is it not working or have I done it wrong. I followed instructions to the letter!

 

The liquid should lighten and go clear, check on top, there should be a yellow switch, that lets you turn the sprayer from watering only, to water and feed.

 

Its been a little while since I used one, we use a big version called a Dosatron, but from customers comments, make sure you fill the pot with feed in with water to the top, hold the sprayer at a 45 degree angle downward to start it off.

 

Thank you. I'll try again.