Hi, I do sympathise with you. We have a Basset Hound who has skin problems. Vets have been really helpful *snorts* they keep up suplied with bottles of anti fungal shampoo at ridiculous prices (ie they make us pay for a proper appointment just to buy the shampoo....£16 becomes £32) & they've never really explained what we might do to try & solve the issue.
Hence I have spent the last year hunting down forums like this to find anyone else who has gone though similar things!

She gets rashy, from what ,we aren't sure...& licks her thighs, scratches her neck. The yeast takes over & we have a nightmare keeping the fur on.
Usually we wash her in Malaseb once a week, currently twice a week as it's been flaring up more lately.
I've also tried other shampoos in between Malaseb as I didn't want to be reliant on that stuff. I used 'Quistel' originally to get the fur grown back after her first bad attack (plucked chicken!!!) which worked but seemed also to encourage yeast growth.
Now I'm using a Neem shampoo all over her which is fab! Her coat is amazing, but I guess the jury is out on whether it helps the itching.

For the rash we use plain old nappy rash cream! Sudocrem works better than tescos own brand though!! It does work straight away.

Sorry I'm rambling on here...
We used to feed her Autarky as it seemed a healthy food like Burns, but more affordable, however last xmas when Nimh was really bad I started learning more about ingredients & discovered that Yeast was added to the food!
We switched to James Wellbeloved & with washing her every 3 days alternating shampoos for about 6 months she was totally fine!
We even managed to go for up to 10 days without her needing to be washed.
But it's gone downhill again & I have no idea why.

We did notice that things like Pigs ears 'may' aggravate it. Also Bonios!
She gets shapes biscuits (3 at bedtime) but they never seem to have been a problem. She ate them even when she was fine.

So now I've been giving her more meat in her diet. I don't want to do the raw thing for many reasons, but I think it's got to be a good idea to add real meat to her diet!!
I've yet to hunt down some bulk buys as yet but the past fortnight she's had chicken mixed with her usual 'greens' (I have a dog that adores spring greens...lol...she's had those for ages with her dinner).
I swap just over a quarter dried food for the chicken & veg.
She wolfs it all down of course, but I've no idea really if the food even makes a difference to her skin problems.

I would like to find something a bit cheaper than JWB but everything I look at that is recomended has added yeast in the ingredients!!