the problem is finding a software sequencer you can get comfortable with. pick one and stick with it, and use it every day. don't give up on a track till you've spent an hour on it, as there's no better practice than finessing an idea you're not sold on to improvement (this will come in handy if you end up doing it for money). with an apt combination of keyboard shortcuts and smart combinations of presets, no amount of software will hold back your ideas from fruition. i use FL studio in this manner to great effect, and can have a 5 minute song assembled to some structure in about 30 minutes. from there it's a matter of EQ and balancing.

another option may be to use something like audiomulch or PD to create the sort of work-flow environment you need to sit down and start sketching.