I use an old fashioned bone handled cake knife. I got 4 of them off Ebay for around 6 pounds. They do the job wonderfully, as they are very thin and quite flexible and haven't snapped. You just wedge it into the crack from the toe and open it up slightly, then add the glue in. Advantage of it being a thin knife is that it can squeeze through the very thin gaps, and also you could use the knife to push the glue into the gap before using the straw method to finish it off. I should start doing youtube uploads of repairs, as I feel that people should learn how to do these things, as it helps them get to know the bat better and take better care of their bat overall. Also saves a few quid!
An alternative to the knife would actually be a spatula used in chemistry labs. Being a Chemical Engineering student, I had to buy one, and found that it was pretty thin and sturdy on the wedge side. (Don't use the scoop side, as it is a little thicker and curved, you may open the crack a little more than intended) Remember to try only open the crack just enough to get the glue deep inside. I was lucky that the work was already mostly done for me by the batsman!
Clamp wise, put something to cushion the back and edges while clamping, as these are vulnerable to dents, if you are using clamps similar to mine of a vice. Would also recommend using two clamps in different directions like I have to improve the fit of the repair. In this case, I used bits of cardboard. Only downside is the cardboard can stick to the bat and rip slightly, but it really isn't much of a bother
The CA here has actually been used for a few net sessions and 2 games now, and the batsman says it is still going strong. Twine is a great idea, just bind like 4 rows of it round the toe with PVA glue, and don't forget to glue over the twine after the glue has set it in place. Also, I would add a little varnish only the cracked area for additional protection against moisture, and make sure to shoe-goo the toe. It will probably help more than a toe guard, and don't be afraid to overlap the goo a few mm onto the face and back, as this will protect the wood when tapping the bat and sliding it in! Just a few tips I feel make a difference!