The fastest F2P way to get level 50 attack from level 41 is to train on hill giants. Use a rune scimitar, rune kiteshield, full rune armour and an inventory of four 4-dose strength potions and ten-fifteen swordfish and four-eight free inventory spaces. These can be killed in the Edgeville dungeon and you can collect their bones and drops for money.
The fastest P2P way to get level 50 attack from level 41 is to train on rock crabs. Use a rune scimitar, rune kiteshield, full rune (including rune boots) and an inventory of four combat potions, one-two shark and the rest of the inventory free for drops. Rock crabs give great xp and rarely hit you so food in not necessary.
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The fastest way of getting level 70 Defense would be Soul Wars 50/50, if it's still going.
Build troops or attack npc
kill 1000 lvl 5 goblines
Easy. Give him or her an Experience Share, then battle a high level pokemon.
If your not cheating, then the fastest way is to buy high level logs and fletch them. Since arrows and bows are sellable you'll be loosing only some of the money.