Very simplistic way (highly effective):

1) Set a parameter you want to study (BB vs. BTN single raised pots).
2) Enter a bet sizing strat along with stacks (would just start with 100BB).
3) Run a script with a significant amount of hands (I see mentions of 180+ boards, but I am not expert on this by any stretch).
4) Pick a board and open it without clicking through the strategy.
5) Go to floattheturn.com or use some other range analyzer that lets you color code (pick parts of your range to bet, pick parts of your range to check, etc. and enter them into the analyzer by color.
6) Check your work. Try to figure out why the solver is doing things differently than you are.
7) If you are having trouble with a spot, post it.

Its much more effective than just looking at grids and trying to memorize stuff. Let repetition of doing it over and over. It's a more effective way to "memorize".

Here is the link to the website I mentioned above.

https://floattheturn.com/wp/tools/range-analyzer/

That, I can not answer (I Use PIO). I am pretty sure GTO+ does scripts but I might be mistaken.

If not, just drop a random flop in an equity program or just pick one and run a sim for that flop and follow the above steps (again, it's very vague and simple way to start). Its learning by practice vs learning by memorization. Practice learning is much more effective

There is also an awesome trainer called Simple GTO Trainer but it could be considered expensive (depending on a persons budget).

To setup script click on run solver --> advanced -> activate database mode

This video covers scripting in GTO+ https://www.youtube.com/watch?v=UTFA77i3trY