My rule is if it didn't come with a ladder then the manufacturer really doesn't want you up there & chances are its a no walk roof. But you can use some plywood on the roof to help spread your weight, the bigger the better for the plywood, feel around to try to locate the rafters and place the plywood to go from rafter to rafter. I would do the crawl method. Also be careful the plywood doesn't slide off the roof with you on it. All this is assuming you aren't an NFL lineman or someone like that size wise. Probably more common problem is wasp nests & other bugs in the outside portion of the A/C than dirt on the fins, next would be bent fins from hail or poor handling during installation.
2018 Durango 318RLT '20 Ford Lariat F350 4X4 Former RVIA Master Tech, ASE Master HD Truck Tech.