I hate fingers. It feels like being poked.
A better way - in my experience as the top, who let another top make love to me was this: approach slowly. Just rub the length of the dick up and down asshhole opening 10-15 times. It feels more like a gentle massage. And maybe he's kissing the back of your neck, too, or rubbing your nipples.
Then, just barely push against the opening for a few seconds (side to side is pleasant). Then try to inset PART of the head (not the whole thing) for a few seconds, then withdraw. do that 5-10 times for a few seconds (maybe up to 5 seconds, or 10 if the partner assents), then withdraw. Each time after that, to in maybe 1/2" more, withdrawing after 5 seconds. Then get the whole head in and FREEZE!!!! Let him get used to it. Maybe move back and forth VERY GENTLY. and then? Withdraw.
By now, it seems like a game, and the partner psychologically gets into it a bit, realizing you're not going to RAM HIM. And that you're actually seducing him and teasing him. That makes it sensual instead of (boringly) sexual (if you're not used to being the bottom, sensual works GREAT for some of us. For most of us, actually, although some guys take to it faster than others).
Then, once you've got the head in, move in an inch or two, kissing his neck (or some other spot that will distract him: nipples (if he's got sensitive ones, are terrific for getting someone hot at the same time there might be the very slightest of pain). Or take your thumbs and dig them (gently) down his biceps (that's a thrill ) starting from the top of the shoulder. or even the shoulder blades (quite nice, as any massage therapist will tell you). or just grip him arms and run your hands up and down them, clamping gently.
By now, he should be mildly to significantly aroused, and you can go further into him. Check in ("is this okay") at each 1/2" of insertion. Move back and forth and then? WITHDRAW. At some point, he's going to indicate - verbally or by body language - "don't pull out." then you go in further and at each step, move in and out and even side to side. Check in again ("Does this feel okay?")
At this point, you're 10-15 minutes into it. Any bottom with anxiety will feel cherished and THAT is what gets him to relax. YMMV, of course. But seduction beats ramming if you're a lover, and not just a 'Sexer.' And by the way? Most guys just know how to have sex. They're unskilled at actual lovemaking.