You can go to www.grand-hirafu.jp and check out the real time camera. Lots of snow now (3 m. at the top). Heard that they were able to ski until May last year due to unusally heavy snow during the winter. Official ski season stops at March 31. So you just have to monitor their snow condition to see if you can ski in April. Have to say, Niseko has the best snow in thw world.
I took a bus from Chitose. It comes pretty frequently and it only took 1 1/2 hours. Very convenient. But I believe the bus opeartes only during the winter so they may not operate in April. I was also there last summer and we rented a car from Chitose. Very nice drive. You can find many local ground service provider through internet. I arranged mine through Niseko Ground Service. They were quite good and car rental through them actually costed lesser than going direct to the car rental company.