Certainly a long way from my local chub waters, never seen the Swale or the Wharfe. The lower reaches of the Dorset Stour and Hants Avon are my local winter patch.
More than a decade ago I decided I just had to have one of the bigger specimens (7lbs+) on the float and have typically concentrated on trotting ever since. It took me until 2012 to finally get one on the float from the Stour and several more have followed over the years. Still haven't quite had one from the Avon.
Trotting a single red maggot on a #20 under a big bit of balsa is my "go to" starting point.
From the previous comments the Swale has an excellent head of chub, and chub are chub!
Apart from location, one major factor is getting the chub to lose some of their natural caution and start feeding freely. If there are numbers of chub in the area, it can sometimes be a great advantage as I think they often react to each other, once one gets its head down, others follow.
Loose feeding accurately, regularly and consistently by hand, catapult &/or dropper is one of the keys. If I can, I will feed to an area quite a way downstream, leaving plenty of room to play the fish between that spot and the net. If that means introducing the feed downstream from me then so be it (particularly if they start coming up to intercept the feed). I usually start to feed as soon as I arrive and while I'm setting up. That may take 20min/30min or more and I often don't start trotting, but keep feeding, for some time after I'm ready to fish.
They can be there straight away, sometimes it takes a while. On my local rivers I know I'm in the right general areas so happy to work a swim with the knowledge the chub can turn on at any time. It's important to feed consistently whether you're catching or not, increasing/decreasing that feeding as you think fit. Some days when I feel the chub are there, I will feed what I call "top & bottom" - at the start and end of the trot - sometimes every trot.
I play around with depth and shotting a lot. Sometimes a simple olivette bulk and a single dropper will work well. I typically use split shot as I can move that around to my hearts content. It also pays to occasionally vary the line of trot. Inside, beyond and further down the line your feeding often produces the better fish. Single red maggot on a #20 beyond the line I'm trying to feed has produced a high proportion of bigger chub.