I may be biased (as you can see) but in my opinion, the best tumbler (mixer) to use right now is Chipmixer. You just need to read the FAQ, it's self-explanatory and quite simple.

If you've already used one as you seem to indicate, then it should be no problem to you. The unique feature with Chipmixer is that it uses "chips" - pre-funded with Bitcoin, so even from the start there's no link to your deposit. There are other options you can do with these chips (merge, split, donate or even bet!) - all off-chain to increase the element of randomness for your privacy. You just use the private keys with each chip any time you want them.

Fees are as low as you want - it uses a donation feature. That's as cheap as it gets with tumblers!

You can PM me or ask in the thread if you need more assistance: https://bitcointalk.org/index.php?topic=1935098