Other browsers exist as well as tools / plug-ins to open tube / PSP files. I would suggest checking out 'Plugin commander' from thepluginsite.com
Create brush from picture tube Open a document less than 500 x 500. Apply picture tubes as required, apply effects as required, and then file > export > custom brush. Give the brush an unique name and set steps / variance / author
Select a brush tool such as airbrush and select the brush from the brush browser and then apply