For once I am in agreement with GoldSaiyan, Trunks is a melee character. You SHOULD fail with him if you use him any other way. Get creative and instead of trying to directly ps, charge Finishing Buster to low power, throw it into the oncoming Kame, then teleport to the side and throw another FB, charged higher. That's about the only way to effectively fight at long ranges with Trunks. Use the fact that you transform faster also; a fully charged and turboed gen beam as an SSJ can overcome a fully charged Kame with enough distance.