I suggest not using this as your primary bottom deal because of the loosening action of the finger. There is simply no way to get rid of it. As Jason England says: "It is a great place to start, but not a great place to end." However, if you choose to stick with it:
1. Work on the rhythm. You speed up whenever you take a bottom. This is common. So, to solve this, either slow down the take on your bottom, or speed up your legitimate deals. Either way, I suggest practicing different speeds on the take. This way, depending on the speed of other players' deals, you can adapt and change speed as needed. It is important to get the rhythm down so you can do the moves as fast or slow as you want. That advice applies to all moves.
2. As "b+w" has mentioned, you take too long to get the deck into an Erdnase grip. Vernon was very big on picking up a deck and immediately getting into the grip. It is talked about in one of his Revelations tapes. If you watch legit gamblers, they do not take any time at all to adjust finger positions etc. They pick up the deck and deal. Another thing Vernon talks about, and I believe said was showed to him by Charlie Miller (I could be wrong) is changing the grip WHILE dealing. You could try starting in mechanic's or full grip, and then switching to an Erdnase grip right before the bottom needs to be done. I don't recommend it though, and it certainly isn't something I would do.
3. Yeah yeah, I know, it's been said before. The Erdnase grip is a tell in itself, as is a straddle grip. No casual player deals cards like this, they use a full grip or (if trained professionally, like a casino or hired dealer) a mechanic's grip. There really isn't any reason for a complete laymen to say "Ooh, an Erdnase grip! He's bottom dealing" However, why give someone the chance to suspect you? I'm not knocking the erdnase, modified erdnase, or straddle deals by the way. I think the Erdnase deals are great and provide the perfect cover for the first or second finger of the right hand to do the dirty work (the take). However, it is something you should be aware of.
4. Your dealing hand dips down whenever a bottom is taken. This is also common, and is even a tell in the hands of experts like Darwin Ortiz and Steve Forte. Try to keep your dealing hand level at all times. I used to do this too, here is what helped me: Practice bottom dealing with the dealing hand flat on the table. After a couple of hours or so, the habit should be gone and you can return to holding the deck above the table. Also: I understand that this action is sometimes done purposely to cover "knuckle flash" or "finger flutter". If you really can't do away with the action, then just make sure to use Erdnase's infamous psychology of uniformity of action. In other words, whenever dealing cards to yourself, even off the top, make sure your hand dips. Again, this is only as a last resort and I highly recommend that you get rid of this tell completely instead.
5. Thumb movement. Probably the hardest tell to get rid of. Your thumb lifts for tops, and is pretty much dead (motionless) for bottoms. This is a big tell. I really can't think of any tips to give you here. It can only be corrected with practice.
I hope these help.