Cupar is the first dog I have excellent recall with. I did use the perfect recall book and forums like this, the perfect recall book was the first dog training book that wasn't regimented, all the books I have on dog training, intimidated me by being so serious and organised. Once I stopped seeing myself as being absolutely useless at dog training and started to relax and enjoy my dogs, my relationship with them changed.
I no longer 'train' my dogs, I now teach them how I want them to behave. I have prioritised what is important to me and recall is one of the highest on my list.
I don't know if this will help but this is how I interact with Cupar on a daily basis and in turn it's working on his recall every single day but it's not a conscious thing more second nature now.
Nearly every time Cupar goes out the door to the garden I recall him at some point as there is usually someone or dog walking past. As soon as he hears his name he races in to the house and stands by the fridge, I keep a bowl of chopped cooked meats just for dogs. He's then allowed back outside once human/dog has passed. This may get repeated a few times in a day as we have a public footpath at the back of our garden. This served two purposes, his recall and prevention of reacting to dogs at the other side of the fence. ( Cassie is a fence barker and I didn't want Cupar doing the same.)
Most of our daily walks are the same one every day. We leave the garden off lead and walk for a few yards and he has been able to sniff and pee for a few minutes then I put him on lead for another five minutes until it's safe to let him off lead again. Once he's let off lead he runs ahead for a few minutes, then checks in with me and I tell him how good he is and tell him to go play. ( I talk a lot and get excited when he checks in, I've been doing this since he was a puppy) Occasionally I will pop his lead on and try some heel walking ( the bloomin bane of my life that's my nightmare) he's then released again and told to go play. At this point he won't leave me for long as he knows the routine, we usually do some sit stays and he gets to play with the ball ( this is the highest of all his rewards). Once the ball goes away I send him off to sniff. He will go further now as he's had his game but I like to keep him on his toes, so I will hide from him and wait for him to find me and he either gets squeezey cheese or very occasionally I will throw the ball once for him.
I still practice his heel walking off lead and on lead for a few minutes, I don't do this to train him in this I do it to interact with him. This is all done not far from home.
Going to new places is similar if he can get off lead, however it's harder with new smells so I do a lot more stop and starts on these walks, Cupar is a runner, he cannot just walk anywhere he has to run but he's also not a confident dog so he will check in and make sure I'm following, I have found if I just stop walking, he will eventually look back, find that I'm further away than he likes and come running back to me, he gets squeezey cheese and lots of praise for this and then released again. Throughout these walks I still pop his lead on and try to get him to walk better on the lead, I then unclip him and tell him to go sniff/play.
The only time I ever recall him, is if I'm 100% sure he will return to me. I did start teaching recall with a whistle but it was just something else to remember to take. So I 'charged' Cupars name in a different tone, it's a Cooooooooopeeeeer and I know it works because it's now been tested on recalling him when he started chasing a hare, more than once.
What I'm hoping you take from this, is it's knowing the dog that you have, find out what he loves the most. Find a way to interact with him you both enjoy. Don't keep calling for Maxx unless you know he's going to come back. Do practice lots at home. Don't stress about having to teach recall at certain times, you don't need two people to teach recall. I never had two people, I had to make do with what I had. If you go somewhere with Maxx that he's likely to run off after someone or something, keep him on a lead. Don't let him off lead until you know he's more interested in you than everything else. I unfortunately now know where I went wrong with most of the dogs I have had, the behaviour I wanted to stop, continued because it was reinforced every time they ran off, whether it was after some child's ball, or another dog.
I have no help from my OH with any of my dogs, in fact walking with my OH has us arguing, as he insists on calling for Cupar to come back every two minutes, he whistles on him, he calls his name and Cupar completely ignores him, on the occasions he does come back my OH thinks it's because he called Cupar, it's not, it's just Cupar checking in with me, so I reward him with squeezey cheese and send him off again, for my OH to start all over again.