You can, but they will never be the same again! So unless it's absolutely necessary, it's better not to clean and reuse them. A good cartomizer will process about 5-9 ml of eliquid, more or less, depending of what kind of ejuice you're using. They are disposable and should be treated as such.
What kind of Smoktech cartos are you using? Single coil? 510 connection? They are pretty good. You may also try 510 Boge cartos; they are harder to fill, as the filler inside is very tightly packed, but they perform well.
These are the different heads I've been comparing on my APV...
From left to right: 1: no name carts packaged as 510D SR (came with APV, rated 3.1 Ohms), 2: Smoktech Cartomizer for DCT U-DCT/510 (dual coil, tried all resistances, preferred 2.9 Ohms), 3: Vivi Nova (tried all resistances, preferred 2.8 Ohms), 4: Joyetech (JT) 510 atomiser (used for dripping only, 1.9 Ohms)
In terms of taste, I much prefer the JT 510 (dripping), then the Vivi Nova, then the Smoktech, then the no-name 510D
If it was convenient, I'd just use the JT 510, but it's not. I'd much prefer to use the Vivi Nova or the tank setup, but neither comes close in terms of taste. I'm not interested in throat hit, but I like lots of vapour. Again, dripping the JT 510 wins here.
NB: My comparisons have been done with fresh equipment, properly infused etc. etc. back to back with the same e-liquid, and adjusted to get the best taste from each setup.
For aesthetic and convenience reasons, I'd really like to get the tank setup performing well, but so far I haven't been able to do so. I just don't know if it's possible to match the taste I get from dripping, but using an alternative device.
Any advice?