WTF is that a carbine in that priming pic 
I don't recommend the runner spraying part of the tutorial. Stick to the old school if you're working with HGUCs and even ACs or anything that involves a lot of exposed cut marks and seamlines, unlike newer PGs and MGs which are almost toy-ish since the parts are easily put together.
Or if you don't want to deal with too much painting, simply cut them out cleanly, sand then panel line
I don't recommend the runner spraying part of the tutorial. Stick to the old school if you're working with HGUCs and even ACs or anything that involves a lot of exposed cut marks and seamlines, unlike newer PGs and MGs which are almost toy-ish since the parts are easily put together.
Or if you don't want to deal with too much painting, simply cut them out cleanly, sand then panel line
