We used the top picture type of one with DS with great success, money well spent. DD on the other hand won't use the steps or the potty. She either climbs up (our toilet is clean but it grosses me out a bit) or I lift her on, I really wish she'd use the steps!!
First few days I put her in a pull up when we did the school run and she went through a stage of pooping in her nappy at the school lol. After a week of that I just ran the gauntlet, we use the toilet at school and I have a little towel in her car seat just in case.
She's still in nappies at night and will poop in it in the morning as still refuses to poop on the toilet despite my best efforts!!