Go to walmart and pick up a bottle of Gesso. If you're in Washington there's a good chance, with tax, It'll be just over $10. I know OR has no tax so that lowers that, as well as they may have things cheaper in general, no ide..Anyway go to the craft section where they have the little bottles of paint and the brushes and so on, you will see a white bottle that is 16oz. It'll say Acrylic Gesso on it. That's literaly the cheapest I ever seen it. Anyway, paint the gesso onto the gunblade (yes it's safe, I've done it, you will see below in a sec) and then you sand that stuff smooth. Sanding will remove quite a bit of it so you may need to repeat a few times but it's well worth it. Then you paint it.Also, if you carved the lion decal into the blade 9which would be way awesome) it'll still show, but you should go into it with black paint just to make it pop..
Here are 2 swords I made with insulation foam that I finished the same way:
Cloud sword:
http://www.cosplay.com/photo/3275474/http://www.cosplay.com/photo/3364063/They are the same sword, but the second one was repainted for another version..
Darui:
http://s88.photobucket.com/user/RazorXCore_2006/media/IMAG0131_zpsb8a98b59.jpg.html
