Here is a link discussing easy ways to raise keel step masts.
viewtopic.php?f=12&t=6937You can either add a small modification to your mast partners that simulates a hinge. Or you can use a small tripod that is the kind of portable solution that you are thinking of. It works without modification to your boat but you need to add something to the version shown if you want to use it without the simulated hinge.
You need to rig something simple, a board or a stiff strap that prevents the mast foot from sliding forward, past the opening of the mast partners while the mast is still horizontal. Once the mast rises the foot will wedge itself in the opening before it is vertical enough to slide down.
It may be that having a helper hold it in place is enough. For what you are planning you would have sufficient manpower. I was using the system singlehandedly. I mostly dispense with the tripod and rely on the simulated hinge instead but I can see that others might benefit from the tripod especially if a helper can guide the mast foot.
The tripod works with a simple purchase of the kind you can find in a hardware store or you can build your own with real blocks from a marine store. No need for any winches.
Good luck!