Sleep training sorta. Question about 5 month old.?

Ok. Here lies the problem. I don't really believe in sleep training but my partner does. We have a 5 month old daughter who cried like crazy every time it comes to naps or bedtime. Hold, rocking, soothing, feeding hasnt worked yet. Were trying to compromise because he's going to be watching her soon and he'll let her CIO when Im at work so Id like her to soothe easier so shes not left alone to cry. So twice now we've left her to fuss. She is tired. We swaddle her (she likes it even at 5 months), give her a pacifier and put her in her cradle. She cries were in there. We pat her and soothe her without picking her up. She actually seems to be less upset then when I try to rock her and feed her. She isnt left to cry alone for very long (30 sec). Do you think this is wrong. Twice now shes went down without to much of a fight. I'm just worried about creating problems with trust. I love her to bits and if snuggling or rocking or feeding worked Id do but it doesn't.