I have Heleniums and have always dead headed with scissors, if I remember them, more or less as the flowers die. Keep up the watering,if needed, and regular feeding to encourage more flowering from below. If you have a great swathe of them it is more difficult. Mine are dotted in clumps. I keep them in order with a discrete tie of string that can be moved up the plant, plus a top dressing round the base to support and keep moisture in. Usually own compost. Split in spring for more plants....they will bloom same year....a wonderful plant.

I usually go over the plants with a pair of shears and cut them back by about a half to two thirds. You do need to cut back as they eventualy get very leggy and bare at the base. Take a few cuttings at the same time as they are quite short lived plants.

Is that what they call the Chelsea Chop Owdboggy? I 've always been too timid to try it. Now I have more clumps dotted about since I split my one big clump I'll give it a go.

Not really, the Chelsea chop is done before things flower to reduce the size of the plant to stop them falling over.
I have one very nice pink one which is cut down to a few inches tall every year, otherwise it blocks the path. However, if you a re not sure about it, then just try it with one clump this year.
One problem I have found is that the older the plant the less you can cut it back, so if your clumps have a lot of bare wood at the base, then do avoid leaving just them as it may not be too keen to shoot from old wood. I replace all mine every 4 years in any case with cuttings from the original plants.