One thing i've noticed with alot of people's painted models is that they don't define well each of the separate features, for example on your mini the teeth are a good example where the bone/white colour has gotten onto both the lips and the recesses between the teeth, if you want a good looking model like GW stuff, just darkline the model.
Everyone has been praising the washes from GW ever since they came out and with good reason, they are awesome materials to darkline in a lazy way because they will settle in the recesses and darken a model so i think try some washes out and tidy up the model, it'll give a great effect on the metallics too. Personally i prefer the inks over washes as i like stronger pigments but the washes do a good job for painters of all skill levels.
PS: don't drybrush the whole model it'll leave a very messy finish in 90% of cases. Just do specific parts like the gun etc.