Agreed, you can use the one you have, even with inversion agitation (which I feel is strongly preferable to using the twirl stick - the stick was intended to get rid of air bells, not to provide agitation). You could pick up a used 2-reel Paterson tank for a song (they're cheap new, too) if you want something a little easier to handle. I've never seen a point to the one-roll tanks since a single roll in a 2-roll tank is more than comfortable enough.

The 2-roll tanks are perfect to do a single roll of 120/220 too.