Thrash the hell out of it.
High revs changing up at the last minute, taking it up to the redline and never changing into top gear. do this for 30 - 60 minutes and it will blow a lot of the crap out of the DPF the problem comes from how blocked it is. If the exhaust gases cannot pass down the channels in the DPF then they can't blow the crap out, like heart attack, but you might at least get some heat into it which will burn off some of the muck and if you can burn enough off you can maybe get the gasses flowing again.
Manual cleaning can be done Wynns sell a fluid for cleaning out DPFs, Commercial operators blow them out with compressed air moving the soot out of the filter and into the lungs of the person cleaning it, that way they can't get back into the filter.