WordNet (r) 3.0 (2006):

soft sell
    n 1: suggestive or persuasive advertising

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "soft sell":
   consumer preference study, consumer research, consumer survey,
   direct-mail selling, hard sell, hawking,
   high-pressure salesmanship, huckstering, jobbing,
   low-pressure salesmanship, mail-order selling, market research,
   marketing, marketing research, merchandising, peddling, promotion,
   retailing, sales campaign, sales promotion, salesmanship, selling,
   sellout, wholesaling