Problem With Step Up

Hi! I have a new budgie and I have gotten him so far to step up on my finger when I have a treat between my fingers. If, on the other hand,  I don't have a treat he does not step up. Most of the time, in this case, I can get my finger just under his belly, but when I try to gently push, he resists. I don't think it would be a good idea to push to hard because he will fall off the perche or escape otherwise, probably leaving him a bad memory with regard to my finger. My question: How can I get him to voluntarily step up on my finger without a treat? His wings are unclipped and he is male and just starting to molt now (so must be around 3 months old, I suppose). Any suggestions? Thanks!