I find patience works best and it is certainly the safest where fingers are concerned. I just plant the seeds, no scarifying necessary, water well and put the flat aside and forget about it. It is usually takes several months but the germination rate is exceptionally high and once the baby cannas have emerged, they grow quickly. I like to use the take out rotisserie chicken containers as mini greenhouses for starting seeds. The lid has perforations to allow air to circulate but they hold in the moisture well also.
I've had good luck with C. patens and C. warscewiczii this way.
