Three flutes are a winner, especially if your mill doesn't have very high spindle speed available. They don't seem any more prone to chip clogging than a 2 flute. I get mine from MariTool. High helix end mills help with chip evac too.
4 flutes and higher can also be used on aluminum, but I would caution in a couple of ways. First, I prefer not to use them at all for slotting where the cutter is totally buried. You're just asking for chip welding. With that said, you can feed them twice as fast as a 2 flute at a given spindle speed, so I like to use them when the cutter isn't completely buried. For example, when edge milling. I also think they give me a little better finish as they effectively multiply the spindle speed versus a two flute.
I am convinced a rougher like the one pictured can evac chips better as can the larger endmills. Still, it's annoying and just a bit scary to weld a 1/2" endmill to the job and snap it off because your CNC is whizzing along in the cut to fast and without good chip evac.
Second, the coolant seems to matter most as lubricant. We HSM's usually don't run fast enough to need "cooling". So choose one that can lubricate and keep those chips from gluing to the cutter. WD-40 is good as is kerosene (lots of that in WD40). Get it in a liquid with a spray bottle, not the aerosol, it's a lot cheaper.
Third, chip evacuation is king. If you can't run flood, get a mister. If you can't mist, run an air stream continuously. If you can't do that, you'd better baby sit.
Fourth, change your feedrate when the endmill is buried. I use a factor of 2/3 of the recommended with a buried cutter so it is feeding slower. That seems to help tremendously. Going around a corner is even touchier in a slot.
Most of the broken endmills I've had were for lack of chip evacuation because I got tired of baby sitting an aluminum job and the cutter was buried. It's amazing how fast those chips build up down in that hole.
You'd be surprised at the feedrates your little HSM mill can do if you get everything set up properly. I have converted my mill to CNC, so I can take advantage of that. Not sure I would care as much on a manual mill, but I do get impatient.