I have grown about 100-120 dahlias for the last 10 years. I lift mine after the first frost. Soil is fairly light so I don't have to dry them out specifically. I keep them in cardboard boxes, without any peat or anything else. I put the boxes in a stable/shed and cover them with fleece and hessian. I lose a few, but not very many, with this process and i top up with a few choice new ones in the spring. In mid April I pot up individually, water, and keep outside. If risk of frost I pop them in the garage overnight, then back outside again. Plant in mid May, as am in southern England. The bed I use has Daffodils in it also, so I have a continuous display of daffs , then dahlias for months. The dahlias are planted on top of the daffs which I don't lift.
I am gradually changing the colour combinations, recently purchasing in your face colours...mauves, orange, red etc...and more and more single flowers to give the bees a chance to enjoy them too. I have also planted up a few larger pots with say 4 of a single variety for impact. These stay in the pots and can be moved around the garden to good effect.
Hope this helps...a worthy plant well worth the effort.
