I can't say I share your experience. Why is using two hands a problem? I always use two hands and it never takes longer than a couple of seconds. Putting a standard condom on a dildo that's well above the average human penis size is equally easy. Putting on a condom on a (partially) flaccid penis is indeed very hard though since you need one hand to hold it and trying to put it on will push the blood out.

Use which size suits you best, but be aware that a looser condoms will cause more slippage.