SHAGGY DOG:A SKINFKINT is a miserly person who has deep pockets and short arms. He, or she, doesn't readily pay for anything if it can possibly be avoided, writes ALBERT JACK.
Skinflints are not poor, they are just mean. In the old days, the term "to skin a flint" was used to describe driving a hard bargain, or making a tight deal. Similar terms used to exist, such as the Latin phrase lana caprina (goat's wool) and the "fleece of an egg". Goats don't have wool, of course, and eggs have no fleece. Each are as meaningless as the skin of a flint (flintstone has no skin), but of the three of them only the word "skinflint" seems to have survived, meaning somebody who would gather and keep worthless items, yet be reluctant to let go of them (ie miserly).
To Trim Your Sails is to reduce your spending, and other activities, in line with your present circumstances. The full version of the nautical idiom is to "trim your sails before the wind". In heavy weather, sailors will reef the sails when the wind is strong and let them out again in calmer waters. It has a similar meaning to the expression "to cut your coat according to your cloth".
To travel on Shank's Pony means to have no transport at all - hence you will be making your way on foot. A variation of this was "to go on shank's mare", which meant the same thing. The shank is the part of the leg below the knee and above the ankle. Everyone has a shank's pony (ie the legs to transport us in place of a pony/horse).
Extracted fromShaggy Dogs and Black Sheep by Albert Jack, Penguin books