another useful tool is a razor saw they come with very fine sharp blades usually with 50 odd teeth to the inch!! you can carefully cut within a thou if you take your time.
Some shipbuilding tricks for waterline kits. While building a 1/700 USS Yorktown, I was getting frustrated getting the color line straight with masking tape, where the hull has compound curves. Light bulb goes off, and I dig out a dial indicator stand, and an X-Acto graphics knife. By very lightly scribing a hair thin line on the hull with the set-up you see, I was able to position the tape accurately along the line. Another light bulb moment. Most of the 1/700 waterline kits came with these metal bars that fit inside the kit. Being tired of sore backs, I drilled the bottom plastic plate and metal bar, and tapped it to match the threads on my photo tripod. Now I could position the ship just about anyway I wanted. Terrific for rigging, painting, etc. Anytime you needed both hands.
Easy way to make ..rubble for a dio or base. Get a bag of redi crete, mix your required amount in a bowl pour on to your garage floor or any smooth surface, when its dry hit with a hammer and you have instant rubble with one flat side. You can fit the pieces back together on your base like a jigsaw puzzle if you want but its easy and looks good.
Here's two things that have helped me a lot with figure painting - - A great paint you can use for priming areas that will be dark is black Vallejo acrylic surface primer. You can find it at most game shops (the ones that deal in miniature gaming) in small squeeze bottles. It is very thin (watery) but it spreads well on most plastics and metals, and the consistency doesn't hide fine details. Plus a little goes a long way - a few drops is all you need for smaller figures. - Ink washes are great to bring out tiny cracks and crags that often blend in. A few daubs allow the wash to settle in these areas and can help make eyes, mouths and creases more noticeable. On very small figures (like 1/72 scale ones), it is often all you need to complete faces.