I have a new spray paint gun and want to spray my wood out door furniture with stain can I put it in the spray paint gun?

And do I have to thinen it out with thinner?

Thanks in advance

I would guess you would need to thin out, i always do even with using a brush, try here :-

http://www.wood-protection.org/newpubs/files/T3Methodsapplyingpreservatives10_05.pdf