I got to ask what are the materials (not sure what is used for Parat)? ABS or PS to the same material then solvent such as MEK / Limonene / Dichloromethane as sold in the Tamiya / EMA etc. bottles, rather than any plastic "cement" from Humbrol or Revell etc. or other "adhesive", is a complete no-brainer. For plastic to something else, or to fill gaps then you have to use some form of bonding / cement. I like the aforementioned Stabilit Express also (often called Stability Express now). I've not had cause to use the "no more nails" / "stixall" / "sticks like s***t" stuff yet, particularly as it's sold in such big tubes compared to what I need but not to say it's no good for some folk in other applications. As other said though, whatever you use: always rough up surfaces as far as possible and de-grease for best results.
Rich