I inherited half a dozen old bushes when I got my plot. One was awful, two were just terrible and the others didn't look too bad. None had been pruned properly for a year or two, so I ignored them the first year as I was having enough fun trying to learn what to plant, then went in with loppers in the winter and pruned out as much dead/old/BigBudded wood as I could. Then left them to regenerate. Some worked well, the bad ones didn't so they got dug up and replaced with raspberries.
I bought a couple of new ones too, with better disease resistance.
I now get a few dozen big buds a year spread over six bushes - I guess this is inevitable - but I get rid of them as soon as I spot them. The newer ones get them too so they're obviously in the allotment site as a whole. Burn or bin the buds.
If the bushes are mostly big bud (which won't grow - this time of year's a good time for a viable/non-viable bud count) then it's best to remove them by gradually circling the bush with a strong fork, excavating the roots and finally lifting it out. Watch your back. If you can't do it right away, prune out all the branches in autumn and dispose of them, and do the digging later.
If you want to give them a chance, prune the whole bush down to the ground after its lost its leaves. It will regrow some branches the season after, which will flower after 2 more years. If *these* have big bud, again it is pretty hopeless, but if they don't, then you've got a regenerated bush which should fruit much better.
moonbells
