The backside noseslide to 270 (frontside) shove-it out is a popular trick as a noseslide variation. It is much harder than the backside shove-it out, but far more skaters seem to prefer this one. Since the board often hits the coping, it is a tough trick, but the key for the landing is keeping your weight slightly outside of the coping and maintaining a stable slide.
You do not necessarily need to have a nollie 360 frontside shove-it mastered beforehand, but a solid backside noseslide is essential.
STEP BY STEP TIPS
1. Approach fast to the well-waxed box

This trick is difficult to do correctly unless you can keep the slide flowing smoothly until the end. That is why it is important to approach with good speed on a well-waxed, slick box. Also, if the box is too low it makes the rotation harder, so try with box at least a foot (about 30cm) high is ideal to give you enough airtime on the out.
2. Keep your balance point outside

This is the most important point of the trick. In a regular noseslide, if you put your weight directly over the coping the board tends to stick, so aiming your weight around the center of the deck helps it slide smoothly. But with the 270 shove-it out, you need to shift your weight even farther outside and keep it there while holding a stable slide—that is the key to making it.
Put forearm forward

This happens naturally, so you do not need to force it, but when doing this trick, extending your front foot in the direction of travel helps you control balance and slide more easily.
3. Drop the tail slightly and push the nose forward

When sliding smoothly into the out, keep your weight to the outside, drop the tail slightly, and push the nose forward firmly with your front foot. You will need to practice the use of the front foot a few times to get the feel, but as mentioned earlier, if your weight shifts even a little toward the nose, the shove-it will not rotate properly and will likely catch on the coping. On the other hand, if your weight is in the correct position and the slide is smooth, the board will spin cleanly.
If you are struggling with the out, focus first on whether you are sliding smoothly before it, and practice calmly. Also, placing your weight slightly toward the back makes the out easier.