Unless you put several practice points into the skill, the only way to get to skill 27 without losing more than one or two platinum is to sharpen rusty weapons. Up until skill 20 or 21, putting a rusty short sword or rusty dagger and a sharpening stone in a forge and clicking combine will increase your skill, change the item from 'rusty' to 'tarnished', and lose you little more than a few copper per attempt. No more sliders. I could have halved the time it took me to get to skill 60 or so by knowing this little trick. Once you get to skill 21, you must use rusty scimitars, rusty spears, etc.
Rusty scimitars are most effective.
Also, it only took about twenty of them to skill up to where they became trivial. Hallard's Resales in East Freeport sells unlimited rusty weapons, so be sure to run by there. Not too painful, and you're already up to skill 26. Now, you create two things. If stacked, you will lose everything you put into the forge, worth about 1 gold.