Tbh, for when i need to make a mix to send to someone I use visual aids to see if they're about the same bpm but I'll manually match them up. But for when I'm just mucking around I'll do it all by ear, usually ends up sloppier but the only way to improve is more practice IMO there isnt really a perfect analogy for it. it's like having training wheels on your bike vs. none - people who can ride without training wheels will have no problem riding one that does have training wheels, but it doesn't work the other way round.