I use X-Mouse for just that. This works with a standard mouse as well as multi buttoned mice. I'll show how to use your left mouse button in lieu of pressing ctrl + left-click.
Download and install X-Mouse
https://www.highrez.co.uk/scripts/downl ... age=XMouse
1) Start Tigers on the Hunt. Alt-Tab out and run X-Mouse (look in your START menu)
2) Click the ADD button
3) Double click on the Tigers on the Hunt application in the list of running apps and then the OK button
4) TotH was added and should be highlighted. If it is not, click it in the panel to do so. The changes we will make are on the right panel once highlighted. Click the Down Arrow (pointed to in the pic) on the Left Button heading and scroll down to Simulated Keys (Undefined) and left click it.

5) Copy and paste the two commands shown into the field at the top. You can also type it in as {CTRL}{LMB}. Click OK, APPLY, then CLOSE.

It's as simple as that. Now when you want to select multiple units in a hex you just click your left mouse button to select the units and do not need to press ctrl and left click each time.
Some menus won't let you click them with this method. When faced with this issue just use your ENTER key instead or just set up the Middle mouse button for standard left click.
Thanks Monkie.
EDIT: With the addition of the shortcut to advance the phase by pressing Space I have found doing the above steps for the middle button and using {SPACE} as the simulated key saves me even more mouse time.