It is important that only the recommended Thinners are used for each application, not doing so, or substituting other proprietary products, will result in a ruined job. Several products have a choice of Thinners depending on the application method you use (ie brush or spray).
Paint can be thinned to improve its flow characteristics and to increase its ability to be absorbed but exceeding the maximum recommended ratio of Thinners can adversely effect the product. When paint is thinned, the spreading rate will increase and the paint will be easier to work with but the dry film thickness will be thinner when the solvents have evaporated and you may need to apply another coat to obtain the required film thickness.
NOTE: In the case of 2 pack products, only the mixed product may be thinned.