I very rarely use head cement, but if I do it is SH clear. I have never found that the head cement makes my flies more durable, However I do use it on quill bodied wet flies along with a counter rib. No doubt the head cement can make a fly look great, but it can also ruin a fly if misplaced. I don't display my flies, so a neat small head and a whip finish and thats good for me.

But for your question about thinners. Laquor thinner, acetone, or denatured alcohol. You can find them all at home depot or lowes in the paint section in little blue cans for under $5. Test the thinner on a small amount of cement to see which one works for your cement. They all have their place on your bench so they are good to have just incase. Good Luck.