If you're new to tabletop wargaming and modelling, you may be getting a little bit confused by the different types of plastics and resins being used to create these miniatures. Tabletop gaming has always been a relatively expensive hobby, and if you're interested in painting and converting miniatures, there are going to be added costs involved. Therefore, it makes sense to understand how different materials are made and how this affects the way you must prepare the models.
Hard plastic is commonly used for miniatures because it's cheap to produce and can be created quickly using moulds as part of the plastic fabrication process. The plastic is created in large vats which heats it up to temperatures that cause it to melt. This can then be injected into moulds at high pressure to reduce the chances of air bubbles. These moulds allow the plastic kits to be created in a very short period of time, before being cooled, packed and processed. This method allows flush fittings and lots of detail, resulting in a high-end products.
Usually plastic models come on a sprue to help protect fragile components, which means they need to be clipped off and cleaned up with a small fine grade file. Washing the plastic in warm soapy water is also a good idea to remove and grease and dirt that may be covering it, which is often a byproduct of the mould release agent. Because the plastic is susceptible to melting through heat and chemical bonds, plastic glue is the best way to build the model. The chemical melts the joins and provides a strong bond.
Resin is a harder substance that is often lighter in colour compared to hard plastic and requires super glue to bond it together. Resin differs because it is usually used for higher quality models that have much more intricate details; therefore, the price is usually higher. Resin needs more preparation, as its covered in releasing agent, which is needed to remove the models from the press moulds.
This releasing agent can once again cause paint to flake off, and so to overcome this, soak the models in warm soapy water and gently scrub with an old toothbrush. During this time you can use the warmth of the water to straighten out any parts of the model that are warped, and gently remove excess resin known as flash, which forms where there are slight gaps in the mould, using a craft knife. As a precaution it's always a good idea to spray your resin models with a light coat of varnish prior to the primer coat, this will cover up any areas of releasing agent that you've missed and help the paint to adhere better.