Thanks Rebel!
One of the things that has really helped me in finding the right rhythm has been drag and drop simplicity in moving loops and having an audible browser preview.After that it comes down to midi editing. Even with those tools it can sometimes be tough to find something that works in a way that jives with a song. I'm sure some artists create songs with the bass and drums first as opposed to having a melody.This is one example of a song I did based on a rhythm
https://soundcloud.com/starise/dirty-dog-2 I did this with BFD 2 and gave the drums an airy sound with the overheads mic setting sends in BFD. I varied it slightly by adding and deleting elements within the drum midi. This is jazzy, but it works with all genres that use drums.
Search features go a long way toward getting a search closer, but sometimes close isn't good enough, especially if you have something in mind already and are trying to find a midi loop to match with it. I've spent hours looking and still not really found a loop I liked and other times it happens within the first 5 minutes.
In the programs I mentioned you can preview your song and hear the loop you choose playing along from your loop browser, so you aren't held to a decision if you decide you don't like a loop.
Depending on your material, it may not be easy or quick. There are companies out there that specialize in unusual drum midi patterns. Odd Grooves come to mind.I have some of their patterns in my library, but even then the beats can be too odd to fit.
Many drum midi loops are played by a real drummer and his emphasis in velocity is transferred to the kit fairly well...so in that case the loops are not usually mechanical sounding, but if they are you can play with the velocity in the midi....and one of the strengths of Sonar is decent midi editing. Lots of folks dread working in a piano roll though, but I think a lot of that is attributed the perception that it might get too technical. In the case of velocity....simply grabbing the velocity and dragging it up or down does the trick.
If I were trying to add loops to a song I already had a melody for I would play to a click track in my chosen tempo and then look at genre specific grooves. If I couldn't find one that fit, then second my choice would be to modify an existing groove that I think is close. It can involve hours if you're picky about your drums. On the other hand, if you're not extremely picky and you are playing say, straight up rock and roll, then things can be much easier....unless you agonize over the finer nuances of a particular kit piece.
If you play only one genre and you've found a drum program and kit you really like, make a template and the next time all that work is already done. Not too long ago Cakewalk had some pre made templates for free download...They might still be available, really a handy thing if you have found something you can live with across a lot of your material.
Good luck Rebel, I hope you find what you're after.