Cellulose should be lacquer. Nitrocellulose lacquer and acrylic lacquer are the common types. Although though the term cellulose points to the nitrocellulose, it is probably more slang now. Acrylic is probably what they mean as the nitrocellulose type is all but phased out in the last 20 years and only was used for pre war car restoration even then. I will also throw a wrench in it or spanner for you. The lacquer thinner that they are recommending is probably the hardware store variety not the auto type. Quality and purity for the auto type, because of the large investment a car paint job is, may make a slight chemistry difference which may be what KK wants. Clear as mud.